Renamed classes should have redirects

**Your Godot version:** 4.1.1

**Issue description:**

If I google for `godot look_at`, the top result is Spatial in Godot 3. When I switch to stable docs, I get "Page not found":
https://docs.godotengine.org/en/stable/classes/class_spatial.html

It would be great for the renamed classes to have a redirect to the new name to make it easier for people coming to godot from search results.

**URL to the documentation page:**

https://docs.godotengine.org/en/stable/classes/class_spatial.html

This page lists all the renames: https://docs.godotengine.org/en/latest/tutorials/migrating/upgrading_to_godot_4.html