Add support for WebSockets over HTTP/2 (#2894)

examples/websockets-http2/assets/index.html

@@ -0,0 +1,7 @@
+<p>Open this page in two windows and try sending some messages!</p>
+<form action="javascript:void(0)">
+    <input type="text" name="content" required>
+    <button>Send</button>
+</form>
+<div id="messages"></div>
+<script src='script.js'></script>

examples/websockets-http2/assets/script.js

@@ -0,0 +1,11 @@
+const socket = new WebSocket('wss://localhost:3000/ws');
+
+socket.addEventListener('message', e => {
+    document.getElementById("messages").append(e.data, document.createElement("br"));
+});
+
+const form = document.querySelector("form");
+form.addEventListener("submit", () => {
+    socket.send(form.elements.namedItem("content").value);
+    form.elements.namedItem("content").value = "";
+});