Broadlink RM Temp Sensor Offset

A simple request to add an offset feature to the existing sensor/broadlink.py component to allow temperature calibration from within the sensor itself, rather than using a separate template sensor (which is a bit of a hack job way to do it).

I know a lot of users here use the RM Pro so will be good to have this implemented, probably the only thing left that it needs as the component and hardware is super reliable.

I do not think this should be part of the Broadlink sensor, since we have the template sensor: https://home-assistant.io/components/sensor.template/