This moves some stuff around to make LibGUI depend on LibSyntax instead
of the other way around, as not every application that wishes to do
syntax highlighting is necessarily a LibGUI (or even a GUI) application.
Rather than creating a TextStyle struct, and then copying its fields
over to a TextAttributes, let's just create a TextAttributes to start
with. This also simplifies the syntax highlighting code by letting us
define underlines along with the other text styling.
This creates folding regions for blocks defined by the following:
- if/elseif/else/endif
- foreach/endforeach
- while/endwhile
- macro/endmacro
- function/endfunction
Since there is no guarantee that each keyword will have a matching
partner, we do our best by looking for the most recent possible start
token matching the current end token. If we find one, we link to it and
drop all the other start-tokens that happened in between. For example,
we would define a folding region for this invalid file like so:
[-] if(TRUE)
│ while()
└─ endif()
