Support keyboard navigation

[thw0rted]

Is your feature request related to a problem? Please describe. Most UI frameworks support a standard set of keys for navigating the UI -- alt+F opens the File menu, arrow keys navigate menu items, Tab moves focus between interactive elements, Enter or spacebar activate buttons, etc etc. This software doesn't do that.

Describe the solution you'd like This software should do that.

Describe alternatives you've considered Lifting my human hand from the keyboard (where it belongs) and operating a pointing device instead, I guess. 😁

Additional context If this is too much time/trouble, please consider adding predefined shortcuts for any (sub)menu items that don't currently have them.