Add PHP 8.1 Support

[patinthehat]

This PR adds PHP 8.1 support to the tests workflow, in addition to the following changes:

• dropped PHPUnit 8 support
• bumped dep versions to latest
• dropped PHP 7.2, 7.3 support
• dropped Laravel 5.8, 6.x, 7.x support
• updated php-cs-fixer workflow & config
• added update changelog workflow
• modified the TestCase class to remove the closure passed to the middleware method after the CaptureReferer::class parameter

This repo needs the primary branch renamed from master to main.

[freekmurze]

Thanks!