Add a guideline for whitespace before inline comments in the GDScript style guide

I think it would be nice to have guidelines about comment whitespace. I use 3 spaces, I've seen people use 1. Calinou recommends 2, the only example in Godot style guide uses 2, many examples throughout the codebase are inconsistent between 1-3. Some of them try to align comments vertically.

I think it would be nice to have some consistency here.

https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript_styleguide.html

I think it would make sense in the "Whitespace" section, something like...

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Use two spaces to separate code from inline comments:

```gdscript
var raw_text = "" # Stores text without markup.
```

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And maybe enforced throughout the documentation.