Documentation: Ray-casting doc mentions shape casting but not explained

**Your Godot version:** 4.3.stable

**Issue description:** As titled, the ray-casting manual mentions:

> One of the most common tasks in game development is casting a ray (**or custom shaped object**) and checking what it hits. This enables complex behaviors, AI, etc. to take place. **This tutorial will explain how to do this in 2D and 3D.**

Currently, it does not explain how to cast a custom shaped object. This was an issue before per #2331 (archived) but apparently not fixed.

The manual should either

- Clarify wording

or

- Include references to the ShapeCast class documentation, examples on how to use them, and the cost/tradeoffs between ray-casting and shape casting and how to approximate per the ray-cast class documentation: https://docs.godotengine.org/en/stable/classes/class_raycast3d.html (unless there _is_ a way to cast a shape with ray-cast that I am not aware of)

I think the latter would greatly benefit beginners, though!

**URL to the documentation page (if already existing):** https://docs.godotengine.org/en/stable/tutorials/physics/ray-casting.html