This commit expands the toml file definition to include
metadata for the origin url, author and name.
A new sync utility fills out that metadata when it pulls from the iterm2
color schemes repo.
The utility also pulls down the scheme data json maintained by
the Gogh project: https://gogh-co.github.io/Gogh/ and converts
it to wezterm's format.
About 50% of Gogh overlaps with iterm2; we take the iterm2 versions
of those schemes by default because the iterm2 data has more info
about things like cursor and selection colors.
The sync utility is responsible for compiling the de-duplicated
set of scheme data into a form that is used by wezterm and its
docs.
