Feature Request: Allow ability to run commands on mute and un-mute

[zepplen]

I'm using a desktop mic with headphones for my setup. I would like to be able to enable "side tones" from the mic to my headphones when it is un-muted.

The easiest way I can think of do achieve this is to be able to define a command that mutebtn can run when ever it mutes or un-mutes.

Ideally in the config file a new option for mute command and un-mute command.

[johntdyer]

This sounds like an amazing add, I would love to send an event to an MQTT broker personally so state could be tracked