Proper MQTT support with example

[kcinnay11]

It would be wonderful if you could include an MQTT example. Similar to the EnviroPlus. https://github.com/pimoroni/enviroplus-python/blob/master/examples/mqtt-all.py

I have tried using the script from https://github.com/jeroenboumans/PimoroniGrowKit-MQTT but unfortunately it always shows me 100% for saturation.

An official example would help a lot.