Add a tip on updating random templates (#15394)

Co-authored-by: Franck Nijhof <git@frenck.dev>

source/_integrations/template.markdown

@@ -339,3 +339,29 @@ sensor:
 ```
 
 {% endraw %}
+
+### Updating templates using `random`
+
+If you use the `random` filter, you may want the template to select a different random element every now and then. If the template does not update automatically due to entity changes it can be updated periodically by using the `homeassistant.update_entity` service with a time pattern automation. For example, this will render a new random number every five minutes:
+
+{% raw %}
+
+```yaml
+sensor:
+  - platform: template
+    sensors:
+      random_number:
+        friendly_name: "Random number"
+        value_template: "{{ range(0,100)|random }}"
+
+automation:
+  - alias: "Update random number template"
+    trigger:
+      - platform: time_pattern
+        minutes: "/5"
+    action:
+      - service: homeassistant.update_entity
+        entity_id: sensor.random_number
+```
+
+{% endraw %}