Internal changes and improvements:
- Run tests on PHP 8.5 too (#22)
- Exclude PHPCS constant type hint checks (#21)
- Bump actions/checkout from 4 to 5 (#20)
- When analyzing tests with PHPStan, extensions need to be specified (#23)
- PHPStan 2.1 & strict rules (#24)
- Test
--prefer-lowest dependencies, too (#25)
