Add Template Sensor device_class support (#5220)

* Add Template Sensor device_class support

* Update battery templates

* Update track battery level example

source/_components/device_tracker.owntracks_http.markdown

@@ -32,7 +32,7 @@ Open OwnTracks and go to Connection preferences:
  - Mode: Select **Private HTTP**
  - Host: [Home Assistant URL]:[port]/api/owntracks/[your name]/[device name]
  - Identification: Turn **Authentication** on, username `homeassistant` and password is your API password that you use to login to Home Assistant.
- 
+
 Host example: If I host my Home Assistant at `https://example.duckdns.org`, my name is Paulus and my phone is a Pixel I would set the host to be `https://example.duckdns.org/api/owntracks/paulus/pixel`. This will result in an entity with an ID of `device_tracker.paulus_pixel`. You can pick any name for the user and the device.
 
 Since the battery data is available as an attribute of the device tracker entity, it can be tracked with a [`template` sensor](/components/sensor.template/).
@@ -47,17 +47,6 @@ sensor:
         friendly_name: Pixel of Paulus
         unit_of_measurement: "%"
         value_template: '{{ states.device_tracker.paulus_pixel.attributes.battery|int }}'
-        icon_template: >-
-          {% set battery_level = states.device_tracker.paulus_pixel.attributes.battery|default(0)|int %}
-          {% set battery_round = (battery_level / 10) |int * 10 %}
-          {% if battery_round >= 100 %}
-            mdi:battery
-          {% elif battery_round > 0 %}
-            mdi:battery-{{ battery_round }}
-          {% else %}
-            mdi:battery-alert
-          {% endif %}
-        entity_id: 
-        - device_tracker.paulus_pixel
+        device_class: battery
 ```
 {% endraw %}

source/_components/sensor.template.markdown

@@ -69,6 +69,11 @@ sensor:
         description: Defines a template for the entity picture of the sensor.
         required: false
         type: template
+      device_class:
+        description: The type/class of the sensor to set the icon in the frontend.
+        required: false
+        type: device_class
+        default: None
 {% endconfiguration %}
 
 ## {% linkable_title Considerations %}