Update model-metadata-schema.json

Added requirement for website url

Author: Annabella-Hines

hub-config/model-metadata-schema.json

@@ -124,6 +124,7 @@
         "methods",
         "methods_long",
         "ensemble_of_models",
-        "ensemble_of_hub_models"
+        "ensemble_of_hub_models",
+        "website_url"
     ]
 }