Add a function to show button mappings using L + LEFT.
Added preliminary error handling that will be improved later to
determine playback issues.
Music is not stopped when an unsupported file is selected.
Some other minor modifications.
TODO:
Pause/play status does not show currently.
Obtain error status of playback thread.
Signed-off-by: Mahyar Koshkouei <deltabeard@users.noreply.github.com>
