Added info about system-settings

README.md

@@ -120,6 +120,16 @@ To disable dashboard app (since it is so corporate):
 
 `abra app cmd <app-name> app run_occ '"app:disable dashboard"'`
 
+## Configuring system settings
+
+All settings on [this page](https://docs.nextcloud.com/server/stable/admin_manual/configuration_server/index.html) can be configured using this command:
+
+`abra app cmd <app-name> app set_system_config <config> '<value>'`
+
+For example, this command sets the default language for new users to Danish:
+
+`abra app cmd <app-name> app set_system_config default_language 'da'`
+
 ## Default user files
 
 - Follow [these docs](https://docs.nextcloud.com/server/latest/admin_manual/configuration_files/default_files_configuration.html) to set the default files list for each user in the Files app