Add some Http3 skeleton

examples/Http3Server.cpp

@@ -0,0 +1,20 @@
+/* Do not rely on this API, it will change */
+#include "Http3App.h"
+#include <iostream>
+
+/* Tentative example of simple Http3 server */
+int main() {
+	uWS::QuicApp({
+	  .key_file_name = "../misc/key.pem",
+	  .cert_file_name = "../misc/cert.pem",
+	  .passphrase = "1234"
+	}).get("/*", [](auto *res, auto */*req*/) {
+	    res->end("Hello quic!");
+	}).listen(3000, [](auto *listen_socket) {
+	    if (listen_socket) {
+			std::cout << "Listening on port " << 3000 << std::endl;
+	    }
+	}).run();
+
+	std::cout << "Failed to listen on port 3000" << std::endl;
+}