Documentation on shortcuts should mention zoom shortcuts

[Proggle]

Your Godot version:
Godot 3.5.1
Issue description:
The documentation doesn't mention the shortcuts for zoom. Specifically

A) Scrolling the mousewheel will zoom in and out
B) Holding down alt and scrolling the mousewheel will zoom in and out to integer zoom levels (needed for pixel art games)
C) pressing 1/2/3/4/5 will jump to predefined zoom levels.

A couple of these features are relatively new and were added in this pull request:

godotengine/godot#50490

I actually got to the point of digging into the codebase to try to figure out how to implement them when I found they already existed.

URL to the documentation page (if already existing):
https://docs.godotengine.org/en/stable/tutorials/editor/default_key_mapping.html?highlight=shortcuts