References to window object crash node scripts using WebsocketProvider

[cristiano-belloni]

Checklist

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Describe the bug
When using WebsocketProvider in a node script, y-websocket.js and lib0 reference window, making the script crash respectively with:

ReferenceError: window is not defined
    at new WebsocketProvider (/.../node_modules/y-websocket/dist/y-websocket.cjs:267:5)

ReferenceError: addEventListener is not defined
    at new LocalStoragePolyfill (node_modules/lib0/dist/broadcastchannel-49d2cc56.cjs:30:5)
    at node_modules/lib0/dist/broadcastchannel-49d2cc56.cjs:51:16
    at Object.setIfUndefined (node_modules/lib0/dist/map-28a001c9.cjs:51:24)
    at getChannel (node_modules/lib0/dist/broadcastchannel-49d2cc56.cjs:49:7)
    at Object.subscribe (node_modules/lib0/dist/broadcastchannel-49d2cc56.cjs:68:32)
    at WebsocketProvider.connectBc (node_modules/y-websocket/dist/y-websocket.cjs:311:10)
    at WebsocketProvider.connect (node_modules/y-websocket/dist/y-websocket.cjs:362:12)
    at new WebsocketProvider (node_modules/y-websocket/dist/y-websocket.cjs:279:12)

To Reproduce
Steps to reproduce the behavior:

1. Run a node script like:

const Y = require("yjs");
const { WebsocketProvider } = require("y-websocket");
const doc = new Y.Doc();

const wsProvider = new WebsocketProvider(
  "ws://localhost:1234",
  "test-room",
  doc,
  { WebSocketPolyfill: require("ws") }
);

2. See error

Expected behavior
No error.

Environment Information

• Node.js
• "y-websocket": "^1.3.9",
• "yjs": "^13.4.12"

Additional context

This code successfully works around the issue:

window = {
  addEventListener: () => null,
};
addEventListener = () => null;