Upgrade deprecated validation rule contract

Changes

• Deprecated hex color validation as Laravel provides that out of the box, see: https://laravel.com/docs/10.x/validation#rule-hex-color.
• Upgrade to the new ValidationRule contract of Laravel which causes a breaking change. The breaking change is limited to the $attribute parameter no longer being provided to the passes() method.
• Use https://github.com/spatie/regex for easier regex usage.

Full Changelog: 4.0.0...5.0.0