Feature Request: add "heater:" option to [temperature_fan]

[s0ybean]

I think this would be a clean way to have curve control for the bed fans if you're already using the chamber_temp sensor for your PTC heater. As of now, a sensor pin needs to be defined for [temperature_fan], and it's not possible to use the same temp sensor for two configs.

[rogerlz]

Thanks for the suggestion. It might make more sense to add the controls to heater_fan.