Update ghost.json (#125)

Add url env variable

template/apps/ghost.json

@@ -9,7 +9,12 @@
             "default": "development",
             "label": "NODE_ENV",
             "name": "NODE_ENV"
-        }
+	},
+	{
+            "default": "http://localhost/",
+            "label": "url",
+            "name": "url"
+	}    
     ],
     "image_arm32": "ghost:latest",
     "image_arm64": "ghost:latest",