Add an example on iterating an array backwards
Add an example on iterating an array backwards

This closes https://github.com/godotengine/godot-docs/issues/3472.

(cherry picked from commit 810d8f06b75cc1762776340aacc2ed6997d2c307)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot