feat(AC): support current_humidity for AC device climate (#411)

* Support `current_humidity` for `climate`

* Cast to None & add comment

* Move from `MideaClimate` to `MideaACClimate`

custom_components/midea_ac_lan/climate.py

@@ -318,6 +318,11 @@ def swing_mode(self) -> str:
         ) + (2 if self._device.get_attribute(ACAttributes.swing_horizontal) else 0)
         return self._attr_swing_modes[swing_mode]
 
+    @property
+    def current_humidity(self) -> float | None:
+        """Midea Climate current humidity."""
+        return cast(float | None, self._device.get_attribute("indoor_humidity"))
+
     @property
     def outdoor_temperature(self) -> float:
         """Midea AC Climate outdoor temperature."""