File name naming conventions inconsistent with engine default file names

[ghost]

Your Godot version:
3.2.4-rc1
Issue description:
The GDScipt style guide reads:

Use snake_case for file names.

But when you click on the script icon in the editor, the default name is the same as the node's name, which should be in PascalCase. This is inconsistent.

URL to the documentation page (if already existing):
https://docs.godotengine.org/en/stable/getting_started/scripting/gdscript/gdscript_styleguide.html#file-names

[Calinou]

Duplicate of godotengine/godot-proposals#1211.