Add Save Facade that will add to config in laravel

I've been using laravel config writer package http://ift.tt/29TxaKO that will edit and save config and I want to add new Facade that will add new (data, value) in config which is always says "Unable to rewrite key "key" in config, does it exist?

I've been add this below code to ConfigWriter\Repository.php

public function toFile($filePath, $newValues, $useValidation = true)
{
    $contents = file_get_contents($filePath);
    $contents = $this->toContent($contents, $newValues, $useValidation);
    file_put_contents($filePath, $contents);
    return $contents;
}

via Chebli Mohamed