Add SwitchEntity to select internal or external sensor

[Simonh98]

Currently, the use of an external temperature sensor is only indicated by a binary_sensor. This small pull request adds the ability to specify the use of the external sensor via a switch.

[kamaradclimber]

Thanks for the contribution, could you also remove the binary sensor definition. It would allow to avoid duplicates.

[Simonh98]

Thanks for the contribution, could you also remove the binary sensor definition. It would allow to avoid duplicates.

Thanks for your feedback. I've removed the corresponding binary_sensor.

[wltng]

Aren't all the switches available as binary sensors (for readonly purposes)?
Besides, removing entities means it is a breaking change. People might have automations running dependent on the removed entity. It might not be a good idea to just remove them.

[kamaradclimber]

I've added a message in the release notes to warn people indeed. Thanks for the remark.