Update vercel.json

Author: ytanck

vercel.json

@@ -4,6 +4,7 @@
     { "source": "/proxy/:match/:url*/", "destination": "https://:match/:url*/" },
     { "source": "/httpproxy/:match/:url*", "destination": "http://:match/:url*" },
     { "source": "/httpproxy/:match/:url*/", "destination": "http://:match/:url*/" },
+    { "source": "/chat", "destination": "https://chat.openai.com/backend-api/conversation" },
     { "source": "/openai", "destination": "https://api.openai.com" }
   ]
 }