No style guide for naming static variables or functions

**Your Godot version:**
4.2.2

**Issue description:**
There is no style guide on naming static variables or functions in `gdscript`.
There is [this mention of static functions and variables](https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript_styleguide.html#methods-and-static-functions) in the Code Order section, but that doesn't actually show an example of a function _or_ variable marked `static`. Nor does it show up in the '[complete class example](https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript_styleguide.html#gdscript-style-guide)'.

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript_styleguide.html