chore: add composer-unused.php

Author: kenjis

composer-unused.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+use ComposerUnused\ComposerUnused\Configuration\Configuration;
+
+return static function (Configuration $config): Configuration {
+    return $config
+        ->setAdditionalFilesFor('codeigniter4/settings', [
+            __DIR__ . '/vendor/codeigniter4/settings/src/Helpers/setting_helper.php',
+        ]);
+};