🩹 Allow parent to be a string (Fixes #79) (#80)

Author: Log1x

src/MenuBuilder.php

@@ -130,7 +130,7 @@ protected function map(array $menu = []): array
     /**
      * Handle the menu item hierarchy.
      */
-    protected function handle(array $items, int $parent = 0): array
+    protected function handle(array $items, string|int $parent = 0): array
     {
         $menu = [];