Add links for alternative libraries into README.md

[nhooyr]

Updates #543

[nhooyr]

@elithrar I know you wanted one liners but I figured since I'd have to point out that golang.org/x/net/websocket is deprecated, might as well have a one line description for mine and gobwas/ws.

[nhooyr]

@elithrar Could you please merge this.

[ghost]

I don't see why this package should list other packages, but if it does, this package should not give opinions about those other packages. Let people judge for themselves.

[nhooyr]

Fair enough. Fixed.

[nhooyr]

I don't see why this package should list other packages

This package is the hub for WebSocket's and Go so its nice to list other packages that may fit peoples needs better or just to be more aware of the ecosystem. Some previous discussion at #543

[nhooyr]

Someone else feel free to pick this up if desired. I'm going to abandon it for now.