Add (un) license

Hi jayjayuk,
thanks for sharing your code. Can you add an license or public domain notice?

Btw. I may found the reason why setting the heater power is not possible: the data-sheet of revision A10 says nothing about the heater power while A20 includes informations about that.
So my conclusion:
A10->firmware v1.0 -> heater only on/off
A20->firmware v2.0 -> heater on/off + power management

Best
