Support navigation using tab and arrow keys and make clickable targets actually send click events

[leozqin]

Is your feature request related to a problem? Please describe.
Broadly, CasaOS does not support navigation using the keyboard.

Specifically:

• The easiest method of navigation for people using screen readers is generally tab navigation, and there does not appear to be any way to select apps from the home page using tab navigation
• An alternative to tab navigation, especially for people with limited dexterity, is to use a keyboard mapping plugin for their browser such as vimium or tridactyl - both of these generate a map of clickable targets, but in CasaOS selecting that clickable target doesn't do anything
• Navigating long pages (such as the app store or lists of files) using up/down arrows or pg up/pg down does not work.

Describe the solution you'd like
CasaOS should support navigation using screen readers and keyboard. In particular, CasaOS should strive to be compliant with Web Content Accessibility Guidelines (WCAG). These particular components of WCAG may be of interest:

• https://www.w3.org/TR/WCAG22/#keyboard-accessible
• https://www.w3.org/TR/WCAG22/#navigable

Describe alternatives you've considered
This isn't really a feature request so much as a request for this project to comply with WCAG standards, but I do notice that Cockpit, which is loosely an alternative to CasaOS, is more compliant and navigable. CasaOS is much more feature-complete though, so I'd rather use CasaOS!

Additional context
This is a great and useful tool, let's make it great and useful for all computer users.