Add outside temperature sensor to OpenTherm component

[BarBaar44]

Component name

OpenTherm

Link to component documentation on our website

https://esphome.io/components/opentherm/

Describe the enhancement

Currently, the component supports enabling Outside Temperature Correction (OTC). However, it's not possible to add a (outside) temperature sensor to the config. OpenThem msgID is 27.

The sensor could, for example, be a Home Assistant sensor.

Use cases

Optimize boiler control and efficiency

Anything else?

This is possible using the OpenTherm gateway in HA: https://www.home-assistant.io/integrations/opentherm_gw/#action-opentherm_gwset_outside_temperature

[github-actions[bot]]

🏷️ I've automatically added the component: opentherm label to help categorize this feature request.