Fixed PHP 8.4 deprecations

[joeworkman]

This fixes the following deprecation warnings with PHP 8.4

Deprecated: Webuni\FrontMatter\FrontMatter::__construct(): Implicitly marking parameter $processor as nullable is deprecated, the explicit nullable type must be used instead in /vendor/webuni/front-matter/src/FrontMatter.php on line 42

Deprecated: Webuni\FrontMatter\Twig\TwigCommentFrontMatter::create(): Implicitly marking parameter $processor as nullable is deprecated, the explicit nullable type must be used instead in /vendor/webuni/front-matter/src/Twig/TwigCommentFrontMatter.php on line 32

Deprecated: Webuni\FrontMatter\Pug\PugCommentFrontMatter::createWithEndComment(): Implicitly marking parameter $processor as nullable is deprecated, the explicit nullable type must be used instead in /vendor/webuni/front-matter/src/Pug/PugCommentFrontMatter.php on line 32

Deprecated: Webuni\FrontMatter\Pug\PugCommentFrontMatter::create(): Implicitly marking parameter $processor as nullable is deprecated, the explicit nullable type must be used instead in /webuni/front-matter/src/Pug/PugCommentFrontMatter.php on line 37

[hason]

@joeworkman Thanks!