Migrate from purescript-dom

[gabejohnson]

The purpose of this PR is to migrate the WebSocket code from purescript-dom to this repository.

[gabejohnson]

@natefaubion a couple of questions:

1. Should I be creating a new effect for sockets?
2. Since the namespacing has changed from DOM.Websocket to Web.Socket, should the type/function names change to follow suit? (WebSocket -> Socket, readWebSocket -> readSocket)

[JordanMartinez]

Based on this comment and this response, I think this PR can be closed? It seems like the intent was to break web-related libraries out into smaller packages when v0.12.0 PS was released, and purescript-web-socket is it's own library now.

[thomashoneyman]

I believe this PR was superseded by c248be2, but please let me know if you’d prefer this be open @gabejohnson!