refactor import

Author: darrachequesne

packages/engine.io/lib/transports/index.ts

@@ -2,7 +2,7 @@ import { Polling as XHR } from "./polling";
 import { JSONP } from "./polling-jsonp";
 import { WebSocket } from "./websocket";
 import { WebTransport } from "./webtransport";
-import { EngineRequest } from "../transport";
+import type { EngineRequest } from "../transport";
 
 export default {
   polling,