Add event to binary sensor example (#18567)

source/_integrations/template.markdown

@@ -299,6 +299,21 @@ curl --header "Content-Type: application/json" \
   http://homeassistant.local:8123/api/webhook/my-super-secret-webhook-id
 ```
 
+### Turning an event into a binary sensor
+
+You can use a trigger-based template entity to convert any event or other automation trigger into a binary sensor. The below configuration will turn on a binary sensor for 5 seconds when the automation trigger triggers.
+
+```yaml
+template:
+  trigger:
+    platform: event
+    event_type: my_event
+  binary_sensor:
+    - name: Event recently fired
+      auto_off: 5
+      state: "true"
+```
+
 ### Sun Angle
 
 This example shows the sun angle in the frontend.