Run custom command on timer start/stop

[levi-jcbs]

Dear developers,

because I always listen to music while working (via Spotify), I came up with the idea of a function to automatically execute a command when the timer starts/stops. For example, I could trigger a script that starts and stops my music playback every time. (You can easily do this with dbus-send). Another advantage of this would be that, in addition to a notification and a sound, you would also be reminded of the end of the (Pomodoro for me) timer by stopping playback or executing other scripts.

Best regards,
Levi