添加vendor扩展包

backend/vendor/symfony/polyfill-mbstring/bootstrap.php

@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+if (\PHP_VERSION_ID >= 80000) {
+    return require __DIR__.'/bootstrap80.php';
+}
+
+return require __DIR__.'/bootstrap72.php';