feat: add websocket support utils, and app handling

[nksaraf]

depends on unjs/listhen#128

adds websocket support by giving a few helpers, highlighted here. This can be added at the top of an event handler, and its a web socket serevr ready to do with all handling logic in your hand.

if (isWebSocketEvent(event)) {
      const wsEvent = toWebSocketEvent(event);
      if (wsEvent.type === "connection") {
        wsEvent.connection.send("pong");
      } else if (wsEvent.type === "message") {
        console.log("got", new TextDecoder().decode(wsEvent.message));
      }
    }
    if (isWebSocketUpgradeRequest(event)) {
      return upgradeWebSocket(event);
    }

[byteab]

@pi0 is there any chance to merge this PR

[pi0]

Thanks for PR. ws is a Node.js dependency and we aim for cross platfom/runtime. Closing for triage.