Register custom rules in proper way

[krzysztofrewak]

Using add(): array from Blumilk\Codestyle\Configuration\Defaults\Rules allows user to add some custom rules. If rule is really custom (not from PHP CS Fixer, this project custom rules set nor kubawerlos/php-cs-fixer-custom-fixers repository), adding it by this method will made configurator fail.

These new rules should be registered by registerCustomFixers() in PhpCsFixerConfig before running.