chore(cli/bench): add ws echo bench (#18595)

cli/bench/websocket/deno_echo.js

@@ -0,0 +1,25 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+
+const port = Deno.args[0] ?? "8080";
+const { serve } = Deno;
+
+function handler(request) {
+  const { socket, response } = Deno.upgradeWebSocket(request, {
+    idleTimeout: 0,
+  });
+  socket.onmessage = (e) => {
+    socket.send(e.data);
+  };
+
+  socket.onopen = () => {
+    console.log("Connected to client");
+  };
+
+  socket.onerror = (e) => {
+    console.log(e);
+  };
+
+  return response;
+}
+
+serve(handler, { port: parseInt(port), hostname: "0.0.0.0" });