enhancement: implement a SoundIcon command

please add to config an option like SoundIconsDir in which user will be able to set an fs dir with sound files, so when user will path sound_icon command selected file will be played using selected output method instead passing this directly to output module.

Start by locating configuration handling for a SoundIconsDir option, then trace dispatch for the sound_icon command and how selected output methods are called. Done means a configured sound file is played through the selected output method rather than being passed directly to the output module.

Written by the indexing model from the issue text.