Shading Language Reference does not describe literals

**Your Godot version:**

4.4

**Issue description:**

Godot 4.4 requires uint in switch statement in a .gdshader, which requires constants and/or literals declared as uint, but there is no discussion in the Godot Shading Language description about literals.

The answer is to use <decimal number>u, but that was only figured out by guessing although looking at the GLSL language definition would give a clue as well.

**URL to the documentation page (if already existing):**

https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html

Start with the Shading Language Reference page linked in the issue and review its discussion of constants and types, then compare the GLSL language definition for literal syntax. Document how numeric literals are written as uint, including the u form, so a reader can use uint values in switch statements without guessing. Done means the page clearly explains this syntax.

Written by the indexing model from the issue text.