Feature Request: Custom AC Temperature
**Describe the idea or improvement**
I have a number of Mi/Aqara AC companions. These work great for control, but in the Home app the reported temperature is just the current set temperature of the AC, not the actual temperature. On Homebridge MIoT, I have a number of devices in the same room which are capable of reporting the temperature of the room. Primarily Mi Air Purifiers.

**Describe the solution you'd like**
It would be great if within miot setting pages I could select the temperature property of another device to replace the room temperature for the AC device within Home. This would significantly improve how the AC controller works in the Home app as it would correctly show ‘TEMP, cooling to SET TEMP’. 

An example of this would be within the miot settings, I could easily select an air purifier already in the same room and already set up with miot to have this device be the temperature reading for the AC, instead of just the ‘set temperature’.

**Additional context**
For the relatively recent Aqara AC Companion device, they achieve a similar thing natively with a linked zigbee temperature and humidity monitor. It would be nice if we could replicate something similar to this with devices already connected and reporting temperature within miot. 