chore: add missing / at the end

It seems better to put / at the end of directories.
See https://getcomposer.org/doc/04-schema.md#psr-4

Author: kenjis

admin/starter/composer.json

@@ -21,7 +21,7 @@
     "autoload": {
         "psr-4": {
             "App\\": "app/",
-            "Config\\": "app/Config"
+            "Config\\": "app/Config/"
         },
         "exclude-from-classmap": [
             "**/Database/Migrations/**"