implement Homeassistant autodiscovery

[dcboy87]

Since this project is used in a lot of homeassistant smart homes it would be great to have the homeassistant autodiscovery feature. In this issue (#299 (comment)) @Henry-Sir has written his own discovery, maybe this is a starting point for @jomjol to integrate this feature

https://www.home-assistant.io/docs/mqtt/discovery/

Thanks a lot for this project!

[caco3]

Good idea, I added #1133 to track it