README: Add known issues

README.md

@@ -28,6 +28,14 @@ Run `docker-compose stop`.
 
 Run `docker-compose stop && docker-compose rm`.
 
+## Known Issues
+
+* Recreating the 'app' container resets the mattermost settings. If you modified
+  settings in System Console or `/mattermost/config/config.json` in the 'app'
+  container and want to keep them, you should manually update `app/config.json`.
+
+* Do not modify the Listen Address in Service Settings.
+
 ## More informations
 
 If you want to know how to use docker-compose, see [the overview