fix: never proxy hot-reload websocket requests

Both create-react-app and vue-cli-service have introduced workarounds for this, but it seems to me that this is always desirable behaviour for webpack-dev-server.

vuejs/vue-cli@72ba750
facebook/create-react-app#7444

Author: ajhyndman

lib/Server.js

@@ -1841,7 +1841,10 @@ class Server {
       (this.server).on(
         "upgrade",
         /** @type {RequestHandler & { upgrade: NonNullable<RequestHandler["upgrade"]> }} */
-        (webSocketProxy).upgrade
+        (req, ...rest) =>
+          req.url !== this.options.webSocketServer.options.path
+            ? webSocketProxy.upgrade(req, ...rest)
+            : null,
       );
     }, this);
   }