Update app.json

Author: kyb3r

app.json

@@ -22,6 +22,10 @@
     "MENTION": {
         "description": "A custom role/user to mention when creating a modmail thread. Default is @here",
         "required": false
+    },
+    "OWNERS": {
+        "description": "Comma seperated user IDs of people that are allowed to use owner only commands. (eval and update)",
+        "required": false
     }
   }
 }