r/frigate: Ensure service starts at boot

Missing a task to enable the *frigate.service* unit meant that the
service would not start automatically when the machine booted.

roles/frigate/tasks/main.yml

@@ -93,7 +93,15 @@
   tags:
   - config
 
-- meta: flush_handlers
+- name: ensure frigate starts at boot
+  service:
+    name: frigate
+    enabled: true
+  tags:
+  - service
+
+- name: flush handlers
+  meta: flush_handlers
 - name: ensure frigate is running
   service:
     name: frigate