Make broadcast channel connection configurable

[ravipati2008]

Broadcast channel is not supported on all platforms(react native for example). So, it would be nice to have an option to disable broadcast channel connections.

_{Huly®: YJS-519}

[dmonad]

Thanks @ravipati2008,

I added an option to disable BroadcastChannel disableBc: true.

This is released in y-websocket@1.4.3.