Add self-check command

docs/maintenance-checking-services.md

@@ -0,0 +1,13 @@
+# Checking if services work
+
+This playbook can perform a check to ensure that you've configured things correctly and that services are running.
+
+To perform the check, run:
+
+```bash
+ansible-playbook -i inventory/hosts setup.yml --tags=self-check
+```
+
+If it's all green, everything is probably running correctly.
+
+Besides this self-check, you can also check your server using the [Federation Tester](https://neo.lain.haus/fed-tester/).