Add sensor device classes (#14010)

homeassistant/components/sensor/linux_battery.py

@@ -94,6 +94,11 @@ class LinuxBatterySensor(Entity):
         """Return the name of the sensor."""
         return self._name
 
+    @property
+    def device_class(self):
+        """Return the device class of the sensor."""
+        return 'battery'
+
     @property
     def state(self):
         """Return the state of the sensor."""