Split off web socket transport into dedicated npm package.

[Simon-Laux]

Because it makes problems when bundling deltachat desktop(deltachat/deltachat-desktop#3171) and it being optional doesn't work for some $reason.
Having separate packages for different Transport implementations is more modular and should prove more stable with bundlers.

[Simon-Laux]

Nodejs meanwhile added native support for web sockets, which means we don't need the extra dependencies anymore.
https://nodejs.org/en/learn/getting-started/websocket

I'll make a PR to use native web sockets instead and remove the dependencies, this way we don't even need an extra package and the web socket transport can stay a part of the yerpc NPM package.