update the config example in the readme

Author: djekl

README.md

@@ -40,13 +40,17 @@ Publish the config file with `php artisan vendor:publish`
 ```php
 
 return array(
-    'storage' => 'session', //session, cache
+    'storage' => 'session', //session, cache, file
 
     // Cache
     // Laravel documentation for more information
     'cache_prefix' => 'moltin_cart_',
     'cache_expire' => '-1', //in minutes, -1  permanent caching
 
+    // Filesystem
+    // Folder Name inside the Storage Path
+    'storage_folder_name' => 'moltin_cart',
+
     // Identifier
     // With a requestcookie (choose for storage: cache, the session will be expired), the cart could be reloaded from a http request, example: the customer could save his cart link (email, hyperlink) and reopen this later.
     // If there is no request, the cookie will be loaded.