Add hvac_action for thermostats

[Macstar1601]

It would be great if you could add the hvac_action to the thermostats so that you can see whether it is heating or cooling. Currently you can't see what the thermostat is doing.

Like this, for example:

https://github.com/albertogeniola/meross-homeassistant/blob/master/custom_components/meross_cloud/climate.py#L20

def hvac_action(self) -> Optional[str]: if not self._device.is_on(): return HVACAction.OFF elif self._device.is_heating: return HVACAction.HEATING elif self._device.mode == HVACAction.COOLING: return HVACAction.COOLING else: return HVACAction.IDLE