Add visuals to explain Vector methods

[Pizzaandy]

Your Godot version: v4.2.1

Issue description:
Godot has some methods in the Vector API with uncommon names: e.g. Slide, Bounce, and Reflect. I have had to explain these methods to both new and experienced developers.

There have already been discussions and PRs about the need to clarify these methods in the docs:
#8286
#7664
godotengine/godot#68392
godotengine/godot#83691
godotengine/godot#11678

There's enough confusion around these methods that adding graphics to the Vector docs is probably justified. It would be nice to point beginners to the docs whenever someone asks about these methods rather than pull out the MS Paint diagram :)

URL to the documentation page (if already existing):
https://docs.godotengine.org/en/stable/classes/class_vector2.html
https://docs.godotengine.org/en/stable/classes/class_vector3.html