Add Alt key as an option for "Activate Hover Zoom"

[Goosegit11]

Is your feature request related to a problem? Please describe.
Currently there's no Alt key option in "Activate Hover Zoom key" setting:

Describe the solution you'd like
Add Alt key as an option.

Describe alternatives you've considered
Imagus mod can do that:

Additional context
Some people might think this is inconvenient because the menu bar appears every time you press Alt, but you can actually disable this behavior by setting ui.key.menuAccessKeyFocuses to false. (That's for Firefox)

[Goosegit11]

#1304 fixes the problem