fix for sf7

[jerome-barbato]

Change Log

Fixed

• Changed declaration of NorbertTech\StaticContentGeneratorBundle\DependencyInjection\Configuration::getConfigTreeBuilder() to be compatible with Symfony\Component\Config\Definition\ConfigurationInterface::getConfigTreeBuilder()
• Changed method signature from `callable $callback = null` to `?callable $callback = null` to explicitly accept null and avoid type errors. Supported since PHP 7.1.

[norberttech]

Thank @jerome-barbato for pointing this out! I took a liberty to also bump minimum required php version to 8.2 will tag new version soon

[jerome-barbato]

My pleasure ! Your plugin helped me a lot ! Thank you