Gamepad support

[NyaomiDEV]

Is your feature request related to a problem? Please describe.
As unconventional as it sounds, I'd like to use Sonixd on my Steam Deck. Right now it requires the use of mouse controls, and while the Deck clearly accomodates for that via mouse emulation, I guess the experience could be better if Sonixd implemented proper gamepad control.

Describe the solution you'd like
Sonixd could implement navigable UI via focus rings and the like (there are libraries out there that you can reuse; for example Discord has one for ReactJS) and then make a gamepad implementation based largely off the focus rings work. This could also be achieved by just emulating keypresses internally and mapping them to gamepad buttons, but this assumes that the UI will be fully navigable with just the keyboard anyway, which brings the focus back to focus rings (pun not intended).

Describe alternatives you've considered
Steam Input button mapping, but it is clunky and cannot ever function properly I'd assume.

Additional context
None really