Add async example

examples/async.php

@@ -0,0 +1,36 @@
+<?php
+
+require __DIR__ . '/../vendor/autoload.php';
+
+use function Amp\async;
+use function Amp\delay;
+
+$future1 = async(function () {
+    delay(1);
+
+    print 'b';
+});
+
+$future2 = async(function () {
+    delay(2);
+
+    print 'c';
+});
+
+$future3 = async(function () {
+    delay(0.5);
+
+    print 'a';
+});
+
+$future1->await();
+$future2->await();
+$future3->await();
+
+delay(1);
+
+print 'd';
+
+delay(1);
+
+print 'e';