Add GDScript Language Data for Markdown Highlighting.

Pulled data from the following pages from the Godot documentation: [All Classes](https://docs.godotengine.org/en/stable/classes/index.html) [@GDScript](https://docs.godotengine.org/en/stable/classes/class_%40gdscript.html) [@GlobalScope](https://docs.godotengine.org/en/stable/classes/class_%40globalscope.html) [GDScript reference](https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript_basics.html) Worth noting: [markdownhighlighter.cpp](https://github.com/pbek/qmarkdowntextedit/compare/develop...DarienMC:qmarkdowntextedit:feature/gdscript_highlighting?expand=1#diff-36d2a396db7785575ce4d5b3993e00a566c113d0245a20ae1ee53a903482a0d3) The method `void MarkdownHighlighter::gdscriptHighlighter(const QString &text)` on line 1717 was created to highlight three items after making use of the existing highlighting systems in place took care of most of it: 1. Highlight `$NodePath` constructs. On GitHub's markdown, it is a little lazy as it only highlights the '$' symbol. My implementation is just as lazy, unfortunately. Ideally, we'd want the whole symbol `$NodePath` to be highlighted like we see in the latest version of Godot Engine 4.3 as seen with the `$AnimationPlayer` below. This likely involves seeking spaces, or periods, or newlines, etc. that I didn't do.  2. Highlight `%UniqueNote` constructs. Same issue as above, but with the '%' symbol. 3. Highlight `@` annotations. So this one is a little weird. I thought it would be sufficient to use the '@' symbol in the language data found in the [qownlanguagedata.cpp](https://github.com/pbek/qmarkdowntextedit/compare/develop...DarienMC:qmarkdowntextedit:feature/gdscript_highlighting?expand=1#diff-2b84467cd1f387ec26227a2be4a6163e7922a78ed04e48cd7b6a207cd7feaf0f) file as an "Other" format. However, the default highlighting does not seem to highlight any `{('@'), QLatin1String("@string")},`. I'm not sure why, but the work-around was to simply add valid annotations in the language data without their '@' symbol, then highlight the '@' on its own.