[Feature Request] Two point calibration

[shyney7]

A feature to compensate the non-linearity of sensor data would be nice for manual calibration. Something like this was implemented in this script to read the data: https://github.com/JsBergbau/MiTemperature2#two-point-calibration

Thanks to @rjblake that mentioned it here how to calibrate the sensor https://github.com/pvvx/ATC_MiThermometer/issues/60#issuecomment-787956694

[pvvx]

This applies to the original firmware - built-in offset of + 5% The stability of the sensor readings also depends on the supply voltage, temperature, and vapor composition. More than + -1% calibration is not possible. The calibration and deviation table is non-linear and two-point snapping gives nothing. The CPU in the thermometer does not have an FPU and on-the-fly correction will require constant expenditures of additional energy, which is better to be transferred to external software on the receiving side.

[Heiko-L]

The uc should have a hardware multiplier so a correction table with linear interpolation would be an alternative to FPU functions.