Improve the pygments lexer to cover GDScript 2 better

[Qubus0]

we've recently updated the gdscript lexer for our own documentation, this is a port of those changes to fit the godot docs

please check as many pages as you can for errors i might have missed.

also let me know if the colors are fine like this. i think some of the existing colors may be from an older theme and not quite up to date, but i didn't touch them for now.

main changes are functions having proper blue color now, global functions being purple, all classes getting the correct greens (including builtins and types having the different green), and proper colors for $String, string names and node paths

[Qubus0]

Side by side screenshot

[Calinou]

Tested locally, it works as expected. Both dark and light theme seem to work.

This is a great start, as it now looks much closer to the Godot script editor (which is the intended goal).

[Qubus0]

Name and Punctuation didn't have css classes yet. adding them makes the () and = bluish, pretty hard to notice, and fixes code in warning callouts being yellow

[Calinou]

Looks great now!

Dark	Light

I can confirm the code color in admonitions is fixed now.

[Qubus0]

singulars done, squashed everything, should be ready - let me know if anything else stands out to you

[Qubus0]

okay, realized most of the light theme colors were outdated, so i brought everything closer to the editor theme. including the yellowed background which the editor doesn't have (improves clarity imo, might split some opinions though)

before	after

[Qubus0]

Updated preview

dark	light
note the function declaration colors above are fixed but	everything below still has the wrong ones but i didn't want to redo everything

[Qubus0]

fixed member vars color and ...args

dark	light

code not changed, just added for simpler screenshot

[Calinou]

I did another test locally and it looks great. Code looks good to me.

[mhilbrunner]

I have concerns about this. It feels like this will grow out of date quickly and would need constant updates. If there is any way at all to automate this part, I'd appreciate it.

[Qubus0]

While I agree automation would be nice (and I'll have a look into it), realistically I don't think this going out of date is much of an issue because

1. The most important classes have had the same name since 4.x, they aren't renamed particularly often.
2. New classes are rarely added to the docs right away
3. Classes are rarely removed between major updates too
4. If there are any outdated classes, the hue will only be off slightly
5. And considering all of that together, the benefit of covering most of the important classes far outweighs risking missing a few less important ones

[mhilbrunner]

Those are some fair points. :) Maybe we can make grabbing the list from that URL during the build a future todo then, and see how it goes.

[mhilbrunner]

Thanks for working on this! Overall it looks quite good to me, besides the single concern noted above.

[mhilbrunner]

Thank you! Merged.

[akien-mga]

Cherry-picked for 4.5.