Add doc URL

CloudronManifest.json

@@ -32,5 +32,7 @@
   ],
   "changelog": "file://CHANGELOG",
   "postInstallMessage": "file://POSTINSTALL.md",
-  "optionalSso": true
+  "optionalSso": true,
+  "minBoxVersion": "1.8.1",
+  "documentationUrl": "https://cloudron.io/documentation/apps/wordpress/"
 }