Add to app.json

Author: fourjr

app.json

@@ -11,6 +11,10 @@
       "description": "The id for the server you are hosting this bot for.",
       "required": true
     },
+    "MODMAIL_GUILD_ID": {
+      "description": "The ID of the discord server where the threads channels should be created (receiving server). Default to GUILD_ID.",
+      "required": false
+    },
     "OWNERS": {
       "description": "Comma separated user IDs of people that are allowed to use owner only commands. (eval).",
       "required": true