🐛 Fix ESM webSocket import issue

We are getting this error when using in ESM enviroment:
```
TypeError: ws.Server is not a constructor
    at expressWs (file:///Users/dawidkisielewski/coding/reedsy/reedsy-editor/node_modules/@reedsy/express-ws/src/index.js:44:20)
    at EditorServer.startWebSocketServer (file:///Users/dawidkisielewski/coding/reedsy/reedsy-editor/packages/server/build/editor-server.js:146:25)
    at EditorServer.start (file:///Users/dawidkisielewski/coding/reedsy/reedsy-editor/packages/server/build/editor-server.js:43:20)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)

```

Author: GitHub Action

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@reedsy/express-ws",
-  "version": "5.0.0-reedsy-3.0.2",
+  "version": "5.0.0-reedsy-3.0.3",
   "description": "WebSocket endpoints for Express applications",
   "exports": {
     "require": {

src/index.js

@@ -5,7 +5,7 @@
 
 import http from 'http';
 import express from 'express';
-import ws from 'ws';
+import { WebSocketServer } from 'ws';
 
 import websocketUrl from './websocket-url.js';
 import addWsMethod from './add-ws-method.js';
@@ -40,7 +40,7 @@ export default function expressWs(app, httpServer, options = {}) {
   // allow caller to pass in options to WebSocketServer constructor
   const wsOptions = options.wsOptions || {};
   wsOptions.server = server;
-  const wsServer = new ws.Server(wsOptions);
+  const wsServer = new WebSocketServer(wsOptions);
 
   wsServer.on('connection', (socket, request) => {
     if ('upgradeReq' in socket) {