[UX improvement]: toxvpn-remote command to notify on connection

[toonn]

I regularly spend some time waiting for a connection to be established. It'd be great if instead of issuing list every 5 minutes in toxvpn-remote I could just issue notify-all or notify friend#0 or something and have it send a BEL character upon succesfully establishing a connection.

👍 for the toxvpn btw, don't know what I'd do without it : )