Netty websockets for Cats Effect

[kamilkloch]

Now that netty streaming is supported by the Cats Effect backend (#3017) (thank you, @kciesielski!) would it be possible to also support websockets for the CE+netty combo? :)

[kciesielski]

@kamilkloch Yes, we'd like to add it as well. The Netty server is now undergoing some config enhancements (with #3056 still pending) and I think that adding WS support will be added in near future. Thanks for creating the ticket.