Allow delete folder have image.

[taimaiduc]

• Operating system : Linux
• Laravel version : 5.5
• Package version : ^1.8
• Steps to reproduce your issue :
• Screenshots of browser console :

vendor/unisharp/laravel-filemanager/src/controllers/DeleteController.php:36

Why dont we allow delete folder ?

if (File::isDirectory($file_to_delete)) {
            if (! parent::directoryIsEmpty($file_to_delete)) {
                return parent::error('delete-folder');
            }

            File::deleteDirectory($file_to_delete);

            return parent::$success_response;
        }

[streamtw]

We just want to prevent accidental deletion. Maybe we can add a new config to disable that check.