[FR] Add setting to define external humidity sensor

[AleXSR700]

Hi everyone,
I only just setup an ESPHome Bluetooth proxy and this eQ-3 integration is impressive!
I especially like the details like defining am external temp sensor for current temp.

As the climate cards allow for temp and humidity, I was wondering if it would be possible to add definition of an external humidity sensor?
I do this for my eQ-3 MQTT setup (current/old implementation if TRV control) and it is really useful.

Would be cool if that were possible :)

Thank you
Alex