Awareness and Doc memory leak

[nemanja-tosic]

Describe the bug

The beforeunload listener isn't removed on destroy, an Awareness instance and a Doc instance are captured via closure and cannot be garbage collected in the browser. See: https://github.com/yjs/y-websocket/blob/master/src/y-websocket.js#L280

To Reproduce

1. Instantiate provider
2. Destroy it
3. Make a memory snapshot and look for retainers of Awareness/Doc

Expected behavior

Awareness/Doc should be garbage collected after destroying the provider.

Environment Information

• Browser

Additional

Memory profile after destroying the provider.