feat: add tests folder with phpstan level 8 solved all errors #167

Job	Run time
PHP-CS-Fixer	7s
PHPStan	21s
check	8s
PHP 8.2 tests (No Symfony specified)	12s
PHP 8.4 tests (No Symfony specified)	17s
PHP 8.1 tests (No Symfony specified)	13s
PHP 8.3 tests (No Symfony specified)	14s
Twig-CS-Fixer	7s
PHP 8.5 tests (No Symfony specified)	14s
PHP 8.1 tests (Symfony 6)	27s
PHP 8.1 tests (Lowest deps)	15s
PHP 8.4 tests (Dev deps)	19s
	2m 54s

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