Revert "Remove axisregistry to make space for the submodule."

This reverts commit 9b890a2eb9.

axisregistry/README.md

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+# GF Axis Registry
+
+This package contains a collection of metadata source files that collectively form the Google Fonts Axis Registry.
+
+The live Axis Registry is at [fonts.google.com/variablefonts](https://fonts.google.com/variablefonts), and axis definitions are only final when they appear on that page.
+
+When the registry is updated here, a line like `axisregistry/axis_name.textproto` should be added to the `to_sandbox.txt` file.
+
+## Axis Metadata Fields
+
+*   `tag`
+    *   Tag for the axis used to specify an axis in `font-variation-settings` and CSS API requests.
+*   `display_name`
+    *   Readable name for the axis, generally the expanded form of `tag`.
+*   `min_value`
+    *   Lower bound of the axis. Inclusive.
+*   `max_value`
+    *   Upper bound of the axis. Inclusive.
+*   `default_value`
+    *   Default position of the aixs.
+*   `precision`
+    *   Describes the specificity at which an axis position can be specified.
+        For example, `0` means values must be specified as whole numbers while `-1` means values can be as precise as one decimal place.
+*   `fallback` (repeated)
+    *   Instance positions along the axis, such as wght 100,200,300,400,500,600,700,800,900.
+    *   A cross-product of fallback positions along all supported axes is created to support legacy browsers that lack variable font support.
+        For axes with CSS3 properties (such as [font-weight](https://drafts.csswg.org/css-fonts-3/#font-weight-prop)), the positions accessible
+        to CSS3 should be specified. For axes lacking CSS3 properties a legacy browser is limited to a single position and that position must
+        be at a fallback.
+*   `fallback_only`
+    *   Describes whether to only use fallback values when presenting to users.
+*   `description`   
+    *   A description of the axis.
+
+## Why does Google Fonts have its own Axis Registry?
+
+We support a superset of the [OpenType axis registry](https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxisreg) axis set, and use additional metadata for each axis.
+Axes present in a font file but not in this registry will not function via our API.
+No variable font is expected to support all of the axes here.
+
+Any font foundry or distributor library that offers variable fonts has a implicit, latent, de-facto axis registry, which can be extracted by scanning the library for axes' tags, labels, and min/def/max values.
+While in 2016 Microsoft originally offered to include more axes in the OpenType 1.8 specification ([github.com/microsoft/OpenTypeDesignVariationAxisTags](https://github.com/microsoft/OpenTypeDesignVariationAxisTags)), as of August 2020, this effort has stalled.
+We hope more foundries and distributors will publish documents like this that make their axes explicit, to encourage of adoption of variable fonts throughout the industry, and provide source material for a future update to the OpenType specification's axis registry.

axisregistry/casual.textproto

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+# CASL based on https://github.com/arrowtype/Recursive#variable-axes
+tag: "CASL"
+display_name: "Casual"
+min_value: 0
+max_value: 1
+default_value: 0
+precision: -2
+fallback {
+  name: "Linear"
+  value: 0
+}
+fallback {
+  name: "Casual"
+  value: 1
+}
+fallback_only: false
+description:
+  "Along this axis, letterforms adjust in stroke curvature, contrast, and"
+  " terminals to go from a sturdy, rational 'Linear' style to a friendly,"
+  " energetic 'Casual' style."

axisregistry/cursive.textproto

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+# CRSV based on https://github.com/arrowtype/Recursive#variable-axes
+tag: "CRSV"
+display_name: "Cursive"
+min_value: 0
+max_value: 1
+default_value: 0.5
+precision: -1
+fallback {
+  name: "Roman"
+  value: 0
+  display_name: "Off"
+}
+fallback {
+  name: "Auto"
+  value: 0.5
+}
+fallback {
+  name: "Cursive"
+  value: 1
+  display_name: "On"
+}
+fallback_only: true
+description:
+  "Controls the substitution of cursive forms along the Slant axis. 'Off' (0)"
+  " maintains Roman letterforms such as a double-storey a and g, 'Auto' (0.5)"
+  " allows for Cursive substitution, and 'On' (1) asserts cursive forms even"
+  " in upright text with a Slant of 0."

axisregistry/fill.textproto

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+tag: "FILL"
+display_name: "Fill"
+min_value: 0.0
+default_value: 0.0
+max_value: 1.0
+precision: -2
+fallback {
+  name: "Normal"
+  value: 0.0
+}
+fallback {
+  name: "Filled"
+  value: 1.0
+}
+fallback_only: false
+description: "The Fill axis is intended to provide a treatment of the design"
+  " that fills in transparent forms with opaque ones (and sometimes interior"
+  " opaque forms become transparent, to maintain contrasting shapes)."
+  " Transitions often occur from the center, a side, or a corner,"
+  " but can be in any direction. This can be useful in animation or"
+  " interaction to convey a state transition. The numbers indicate"
+  " proportion filled, from 0 (no treatment) to 1 (completely filled)." 

axisregistry/flair.textproto

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+tag: "FLAR"
+display_name: "Flair"
+min_value: 0.0
+default_value: 0.0
+max_value: 100.0
+precision: 1
+fallback {
+  name: "Normal"
+  value: 0.0
+}
+fallback {
+  name: "Flair"
+  value: 100.0
+}
+description: 
+  "As the flair axis grows, the straight sans serif terminals develop"
+  " a swelling, and joints become more idiosyncratic. Originally referring"
+  " to the flaring of the stems, Flair stands for style and panache."

axisregistry/grade.textproto

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+# GRAD based on https://github.com/TypeNetwork/Opentype-1.8-Axis-Proposal/blob/gh-pages/proposal/Grade/ProposalSummary.md
+tag: "GRAD"
+display_name: "Grade"
+min_value: -1000
+max_value: 1000
+default_value: 0
+precision: 0
+fallback {
+  name: "Normal"
+  value: 0
+}
+fallback_only: false
+description:
+  "Finesse the style from lighter to bolder in typographic color, by varying"
+  " stroke thicknesses or other forms, without any changes overall width,"
+  " inter-letter spacing, or kerning, so there are no changes to line breaks"
+  " or page layout. Negative grade makes the style lighter, while positive"
+  " grade makes it bolder. The units are the same as in the Weight axis."

axisregistry/italic.textproto

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+# ital based on https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_ital
+tag: "ital"
+display_name: "Italic"
+min_value: 0
+max_value: 1
+default_value: 0
+precision: -1
+fallback {
+  name: "Roman"
+  value: 0
+}
+fallback {
+  name: "Italic"
+  value: 1
+}
+fallback_only: true
+description:
+  "Adjust the style from roman to italic. This can be provided as"
+  " a continuous range within a single font file, like most axes, or as a"
+  " toggle between two roman and italic files that form a family as a pair."

axisregistry/monospace.textproto

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+# FOR TESTING ONLY [for now anyway]
+# MONO based on https://github.com/arrowtype/Recursive#variable-axes
+tag: "MONO"
+display_name: "Monospace"
+min_value: 0
+max_value: 1
+default_value: 0
+precision: -2
+fallback {
+  name: "Proportional"
+  value: 0
+}
+fallback {
+  name: "Monospace"
+  value: 1
+}
+fallback_only: false
+description:
+  "Adjust the style from proportional (natural widths, default) to"
+  " monospace (fixed width). Monospace is when all glyphs have the same"
+  " total character width, and more wide or narrow letter proportions to fill"
+  " the space such as a narrower 'w' or wider 'r.' Proportionally spaced"
+  " fonts have letters drawn with more typical proportions, and each glyph"
+  " takes up a unique amount of space on a line."

axisregistry/optical_size.textproto

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+# opsz based on https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_opsz
+# fallbacks based on https://en.wikipedia.org/wiki/Traditional_point-size_names
+# plus discussion with dcrossland@
+tag: "opsz"
+display_name: "Optical size"
+min_value: 6
+max_value: 144
+default_value: 14
+precision: -1
+fallback {
+  name: "6pt"
+  value: 6
+}
+fallback {
+  name: "7pt"
+  value: 7
+}
+fallback {
+  name: "8pt"
+  value: 8
+}
+fallback {
+  name: "9pt"
+  value: 9
+}
+fallback {
+  name: "10pt"
+  value: 10
+}
+fallback {
+  name: "11pt"
+  value: 11
+}
+fallback {
+  name: "12pt"
+  value: 12
+}
+fallback {
+  name: "14pt"
+  value: 14
+}
+fallback {
+  name: "16pt"
+  value: 16
+}
+fallback {
+  name: "17pt"
+  value: 17
+}
+fallback {
+  name: "18pt"
+  value: 18
+}
+fallback {
+  name: "20pt"
+  value: 20
+}
+fallback {
+  name: "24pt"
+  value: 24
+}
+fallback {
+  name: "28pt"
+  value: 28
+}
+fallback {
+  name: "36pt"
+  value: 36
+}
+fallback {
+  name: "48pt"
+  value: 48
+}
+fallback {
+  name: "60pt"
+  value: 60
+}
+fallback {
+  name: "72pt"
+  value: 72
+}
+fallback {
+  name: "96pt"
+  value: 96
+}
+fallback {
+  name: "120pt"
+  value: 120
+}
+fallback {
+  name: "144pt"
+  value: 144
+}
+fallback_only: false
+description:
+  "Adapt the style to specific text sizes, specified in Points. At smaller"
+  " sizes, letters typically become optimized for more legibility, with loose"
+  " spacing/kerning and thicker strokes with less detail. At larger sizes,"
+  " letters are typically optimized for headlines with thinner strokes and"
+  " more detailed forms, and more extreme weights and widths. When used in"
+  " CSS, this axis is activated by default, but not all products/platforms"
+  " use it automatically."

axisregistry/slant.textproto

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+# slnt based on https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_slnt
+tag: "slnt"
+display_name: "Slant"
+min_value: -90
+max_value: 90
+default_value: 0
+precision: 0
+fallback {
+  name: "Default"
+  value: 0
+}
+fallback_only: false
+description:
+  "Adjust the style from upright to slanted, also known to typographers"
+  " as an 'oblique' style. Rarely, slant can work in the other direction,"
+  " called a 'backslanted' or 'reverse oblique' style."

axisregistry/softness.textproto

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+# SOFT based on https://github.com/undercasetype/Fraunces#variable-axes
+tag: "SOFT"
+display_name: "Softness"
+min_value: 0
+max_value: 100
+default_value: 0
+precision: -1
+fallback {
+  name: "Sharp"
+  value: 0
+}
+fallback {
+  name: "Soft"
+  value: 50
+}
+fallback {
+  name: "SuperSoft"
+  value: 100
+}
+fallback_only: false
+description: "Letterforms become more soft and rounded."

axisregistry/volume.textproto

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+tag: "VOLM"
+display_name: "Volume"
+min_value: 0.0
+default_value: 0.0
+max_value: 100.0
+precision: 1
+fallback {
+  name: "Normal"
+  value: 0.0
+}
+fallback {
+  name: "Loud"
+  value: 100.0
+}
+description:
+  "Transforms serifs from glyphic to wedge shapes,"
+  " and adds a little more edge to other details."

axisregistry/weight.textproto

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+# wght based on https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_wght
+tag: "wght"
+display_name: "Weight"
+min_value: 1
+max_value: 1000
+default_value: 400
+precision: 0
+fallback {
+  name: "Thin"
+  value: 100
+}
+fallback {
+  name: "Extra Light"
+  value: 200
+}
+fallback {
+  name: "Light"
+  value: 300
+}
+fallback {
+  name: "Regular"
+  value: 400
+}
+fallback {
+  name: "Medium"
+  value: 500
+}
+fallback {
+  name: "Semi Bold"
+  value: 600
+}
+fallback {
+  name: "Bold"
+  value: 700
+}
+fallback {
+  name: "Extra Bold"
+  value: 800
+}
+fallback {
+  name: "Black"
+  value: 900
+}
+fallback_only: false
+description:
+  "Adjust the style from lighter to bolder in typographic color, by varying"
+  " stroke thicknesses or other forms. This typically changes overall width,"
+  " and so may be used in conjunction with axes for Width and Grade (if"
+  " present)."

axisregistry/width.textproto

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+# wdth based on https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_wdth
+tag: "wdth"
+display_name: "Width"
+min_value: 25
+max_value: 200
+default_value: 100
+precision: -1
+# Instance values based on https://docs.microsoft.com/en-us/typography/opentype/spec/os2#uswidthclass
+fallback {
+  name: "Super Condensed"
+  value: 25
+}
+fallback {
+  name: "Ultra Condensed"
+  value: 50
+}
+fallback {
+  name: "Extra Condensed"
+  value: 62.5
+}
+fallback {
+  name: "Condensed"
+  value: 75
+}
+fallback {
+  name: "Semi Condensed"
+  value: 87.5
+}
+fallback {
+  name: "Normal"
+  value: 100
+}
+fallback {
+  name: "Semi Expanded"
+  value: 112.5
+}
+fallback {
+  name: "Expanded"
+  value: 125
+}
+fallback {
+  name: "Extra Expanded"
+  value: 150
+}
+fallback {
+  name: "Ultra Expanded"
+  value: 200
+}
+fallback_only: false
+description:
+  "Adjust the style from narrower to wider, by varying the proportions of"
+  " counters, stems, and other forms including overall spacing and kerning."
+  " This typically changes the apparent weight (what typographers call"
+  " 'typographic color') in a subtle way, and so may be used in conjunction"
+  " with axes for Width and Grade (if present)."

axisregistry/wonky.textproto

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+# WONK based on https://github.com/undercasetype/Fraunces#variable-axes
+tag: "WONK"
+display_name: "Wonk"
+min_value: 0
+max_value: 1
+default_value: 0
+precision: 0
+fallback {
+  name: "Non Wonky"
+  value: 0
+}
+fallback {
+  name: "Wonky"
+  value: 1
+}
+fallback_only: true
+description:
+  "Binary axis to control the subsitution of wonky forms along the"
+  " optical size axis. 'Off' (0) maintains more normalized letterforms,"
+  " such as the leaning n/m/h in roman, or the bulbous flags in the"
+  " b/d/h/k/l of the italic."
+  " In static fonts, this is also available as an OpenType Stylistic Set."

axisregistry/x_opaque.textproto

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+# XOPQ based on https://variationsguide.typenetwork.com/#xopq
+tag: "XOPQ"
+display_name: "X opaque"
+min_value: -1000
+max_value: 2000
+default_value: 88
+precision: 0
+fallback {
+  name: "Normal"
+  value: 88
+}
+description:
+  "Assigns a 'black' per mille value to each instance of the design space."

axisregistry/x_transparent.textproto

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+# XTRA based on https://variationsguide.typenetwork.com/#xtra
+tag: "XTRA"
+display_name: "X transparent"
+min_value: -1000
+max_value: 2000
+default_value: 400
+precision: 0
+fallback {
+  name: "Normal"
+  value: 400
+}
+description:
+  "Assigns a 'white'”' per mille value to each instance of the design space."

axisregistry/x_transparent_figures.textproto

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+# XTFI based on https://variationsguide.typenetwork.com/#xtfi
+tag: "XTFI"
+display_name: "X transparent figures"
+min_value: -1000
+max_value: 2000
+default_value: 400
+precision: 0
+fallback {
+  name: "Normal"
+  value: 400
+}
+description:
+  "Assigns a 'white' per mille value to each instance of the design space."

axisregistry/y_opaque.textproto

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+# YOPQ based on https://variationsguide.typenetwork.com/#yopq
+tag: "YOPQ"
+display_name: "Y opaque"
+min_value: -1000
+max_value: 2000
+default_value: 116
+precision: 0
+fallback {
+  name: "Normal"
+  value: 116
+}
+description:
+  "Assigns a 'black' per mille value to each instance of the design space."

axisregistry/y_transparent_ascender.textproto

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+# YTAS based on https://variationsguide.typenetwork.com/#ytas
+tag: "YTAS"
+display_name: "Y transparent ascender"
+min_value: 0
+max_value: 1000
+default_value: 750
+precision: 0
+fallback {
+  name: "Normal"
+  value: 750
+}
+description:
+  "Assigns a 'white' per mille value to each instance of the design space."

axisregistry/y_transparent_descender.textproto

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+# YTDE based on https://variationsguide.typenetwork.com/#ytde
+tag: "YTDE"
+display_name: "Y transparent descender"
+min_value: -1000
+max_value: 0
+default_value: -250
+precision: 0
+fallback {
+  name: "Normal"
+  value: -250
+}
+description:
+  "Assigns a 'white' per mille value to each instance of the design space."

axisregistry/y_transparent_figures.textproto

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+# YTFI based on https://variationsguide.typenetwork.com/#ytfi
+tag: "YTFI"
+display_name: "Y transparent figures"
+min_value: -1000
+max_value: 2000
+default_value: 600 # this is NOT what TN defined, it's just a value that fits for Roboto Flex
+precision: 0
+fallback {
+  name: "Normal"
+  value: 600
+}
+description:
+  "Assigns a 'white' per mille value to each instance of the design space."

axisregistry/y_transparent_lowercase.textproto

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+# YTLC based on https://variationsguide.typenetwork.com/#ytlc
+tag: "YTLC"
+display_name: "Y transparent lowercase"
+min_value: 0
+max_value: 1000
+default_value: 500
+precision: 0
+fallback {
+  name: "Normal"
+  value: 500
+}
+description:
+  "Assigns a 'white' per mille value to each instance of the design space."

axisregistry/y_transparent_uppercase.textproto

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+# YTUC based on https://variationsguide.typenetwork.com/#ytuc
+tag: "YTUC"
+display_name: "Y transparent uppercase"
+min_value: -1000
+max_value: 1000
+default_value: 500
+precision: 0
+fallback {
+  name: "Normal"
+  value: 725
+}
+description:
+  "Assigns a 'white' per mille value to each instance of the design space."