New template sensor attributes docs (#10204)

* Updated documentation for template sensor with attributes

* Update template.markdown

Fix documentation

source/_components/template.markdown

@@ -68,6 +68,15 @@ sensor:
         description: Defines a template for the entity picture of the sensor.
         required: false
         type: template
+      attribute_templates:
+        description: Defines templates for attributes of the sensor.
+        required: false
+        type: map
+        keys:
+          "attribute: template":
+            description: The attribute and corresponding template.
+            required: true
+            type: template
       device_class:
         description: Sets the class of the device, changing the device state and icon that is displayed on the UI (see below). It does not set the `unit_of_measurement`.
         required: false
@@ -246,6 +255,38 @@ sensor:
 ```
 {% endraw %}
 
+### Add Custom Attributes
+
+This example shows how to add custom attributes.
+
+{% raw %}
+```yaml
+sensor:
+  - platform: template
+    sensors:
+      my_device:
+        value_template: >-
+          {% if is_state('device_tracker.my_device_nmap','home') %}
+            Home
+          {% else %}
+            {{ states('device_tracker.my_device_gps') }}
+          {% endif %}
+        attribute_templates:
+          latitude: >-
+            {% if is_state('device_tracker.my_device_nmap','home') %}
+              {{ state_attr('zone.home','latitude') }}
+            {% else %}
+              state_attr('device_tracker.my_device_gps','latitude')
+            {% endif %}
+          longitude: >-
+            {% if is_state('device_tracker.my_device_nmap','home') %}
+              {{ state_attr('zone.home','longitude') }}
+            {% else %}
+              {{ state_attr('device_tracker.my_device_gps','longitude') }}
+            {% endif %}
+```
+{% endraw %}
+
 ### Working without entities
 
 The `template` sensors are not limited to use attributes from other entities but can also work with [Home Assistant's template extensions](/docs/configuration/templating/#home-assistant-template-extensions).