Bundle new maintenance-mode command

Author: schlessera

composer.json

@@ -23,6 +23,7 @@
         "wp-cli/i18n-command": "^2",
         "wp-cli/import-command": "^2",
         "wp-cli/language-command": "^2",
+        "wp-cli/maintenance-mode-command": "^2",
         "wp-cli/media-command": "^2",
         "wp-cli/package-command": "^2",
         "wp-cli/rewrite-command": "^2",