Update to Godot 4 and highlight.js 11

[Calinou]

trafficstars

Note that I couldn't get the ES module build to work in the browser, so maybe we should remove it.

• This closes #9 and #10 by superseding them.

Testing project: highlightjs-gdscript-test.zip Change the path to dist/gdscript.min.js in index.html to match a location on disk, then open index.html in a web browser. No build step needed.

Preview

Using vs2015 theme and the test project linked above.

[joshgoebel]

Please do the "upgrade" work in an isolated commit (that doesn't move the file around) so I can properly review the changes.

[Calinou]

Please do the "upgrade" work in an isolated commit (that doesn't move the file around) so I can properly review the changes.

Done (it turns out we don't need to move any files after rebasing on master).