* add phpunit as a dev dependency

* add some basic tests for UrlHelper::rewrite_relative()
 * fix UrlHelper::rewrite_relative() to work better on non-absolute
   relative URL paths

vendor/phpunit/php-timer/src/Timer.php

@@ -0,0 +1,40 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-timer.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\Timer;
+
+use function array_pop;
+use function hrtime;
+
+final class Timer
+{
+    /**
+     * @psalm-var list<float>
+     */
+    private $startTimes = [];
+
+    public function start(): void
+    {
+        $this->startTimes[] = (float) hrtime(true);
+    }
+
+    /**
+     * @throws NoActiveTimerException
+     */
+    public function stop(): Duration
+    {
+        if (empty($this->startTimes)) {
+            throw new NoActiveTimerException(
+                'Timer::start() has to be called before Timer::stop()'
+            );
+        }
+
+        return Duration::fromNanoseconds((float) hrtime(true) - array_pop($this->startTimes));
+    }
+}