Added check for php server.

Added an if check that allows the built-in PHP server to serve existing files directly.
On a server it's handled by nginx, purely for ease of development.

index.php

@@ -1,5 +1,10 @@
 <?php declare(strict_types=1);
 
+// For server.sh and php -S localhost
+if (PHP_SAPI === 'cli-server' && is_file(__DIR__ . parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH))) {
+    return false;
+}
+
 define('ROOT', __DIR__);
 require ROOT . '/src/bootstrap.php';
 require ROOT . '/src/router.php';