Set memory limit to 300mb

CloudronManifest.json

@@ -16,5 +16,6 @@
   "website": "https://nodebb.org/",
   "contactEmail": "support@cloudron.io",
   "icon": "logo.png",
-  "mediaLinks": [ ]
+  "mediaLinks": [ ],
+  "memoryLimit": 314572800
 }