WIP: provide WebSocket support via http4s

[kubukoz]

At the moment, usage looks like this:

// in IOApp
override def run(
  args: List[String]
): IO[ExitCode] = {
  import com.comcast.ip4s._
  EmberServerBuilder
    .default[IO]
    .withPort(port"30000")
    .withHttpWebSocketApp { ws =>
      HttpApp.liftF {
        ws.build { in =>
          fs2
            .Stream
            .resource(mkServer)
            .flatMap {
              langoustine.http4s.WebSocketServer.make(_, bufferSize = 2048).apply(in)
            }
        }
      }
    }
    .build
    .useForever
}

def mkServer: Resource[IO, LSPBuilder[IO]]

it's much nicer if you don't have per-connection resources , I'll tell you that...

Perhaps something like a WebSocketLangoustineApp should also be provided, but I suppose people might want to have the ability to configure WebSocketBuilder2 on their own.