Nice to have: trigger MQTT autodiscovery / configuration menu

[mcarbonne]

Currently, there is no way to trigger an MQTT autodiscovery message. It would be nice to have a dedicated "config" menu, allowing to :

• trigger autodiscovery
• enter setup
• enter wifi setup
• perform a factory reset
• reboot ? It might even replace the "10s/20s/30s" press behaviors.

This weekend, after an update of my MQTT broker, I had some issues with home assistant so I had to remove some devices. It appears that there is currently no easy way to trigger the autodiscovery. Looking at the code, I found only 2 methods:

• perform a factory reset
• update the firmware

[nplan]

The config menu is a great idea. Will implement in the future.

The autodiscovery message can actually be triggered this way:

1. Hold any button for 10s to enter setup
2. Immediately press a button to exit the setup
3. The autodiscovery message will be sent the next time network connects (either button press or timer wakeup)

[nplan]

Settings menu added in v2.1.0. The discovery message can be triggered by restarting the device. It's published on the next button press after the restart.