option to allow use of mpv default keyboard shortcuts: volume, stop, start, etc.

[pcleddy]

hello, i've got option to allow mpv commands w some simple changes

i used a flag --controls. seems could be better.

any preference on this flag name before i submit PR? (not that you'll like or accept it :))

--keyboard-shortcuts? seems long.

https://github.com/pcleddy/somafm-cli/commit/4ef4cbf3b86dfaa0344941a5999f59980420b4da

[bvvt]

That would be very useful, theres no way to pause or to change station once you play one :(