Allow leaving queue to not break other user's games

app.py

@@ -289,7 +289,14 @@ async def quick_match(request: Request):
                 return JSONResponse({"room_id": quick_map[qid]})
             else:
                 return JSONResponse({})  # Client handles empty as continue to wait
-
+        elif (
+            data
+            and len(data) == 2
+            and "queue_id" in data
+            and data["queue_id"] in quick_queue
+            and "leave" in data
+        ):
+            quick_queue.remove(data["queue_id"])
         else:
             qid = str(uuid.uuid4())
             quick_queue.append(qid)