Core: Add climate support to Google Assistant component

[sibbl]

As introduced today in version 0.56, we now have a Google Assistant actions component which can be used to control many things, but no thermostats.

Google also supports Smart Home Thermostats, which should make it possible to control climate devices using Google Assistant: https://developers.google.com/actions/smarthome/guides/thermostat and https://developers.google.com/actions/smarthome/traits/temperaturesetting

It should be possible to set both modes+temperatures (Google also lets users enter ranges) as well as only temperatures (when there are no modes supported, like on some Zwave climate devices), using Google Assistant.

[Dheeraj1998]

Hi! I would love to work on this issue but would need some guidance being a beginner. Could you help me out to work on this problem @sibbl?

Thank you 😃

[sibbl]

@Dheeraj1998 although I'm a software developer, Python was never my biggest friend... So please don't see me as an active developer over here ;) I'm sure there are some docs about how to start developing with HA and for this specific issue, I bet this is where most the implementation should happen: https://github.com/home-assistant/home-assistant/blob/master/homeassistant/components/google_assistant/smart_home.py

[emosenkis]

I'm almost ready to submit a pull request for this (I need to finish writing tests and, ideally, test it for real against Google's API)