Add some info in the readme how to refresh the ai thermostat entities from the config file

[RubenKelevra]

We currently just assume that the user knows that they can reload the ai thermostat entities from the config file without restarting HA.

I think that's quite uncommon for a custom component and should be mentioned in the readme.

@KartoffelToby feel free to self assign :)

Should be tackled after #156 and is somehow related to #151

[Se7enair]

and dont forget to change the button name to better_thermostat. It's still saying ai_thermostat.

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This issue has been automatically marked as stale because it has not had recent activity.