ReadMe Update - PHPStan Level 6 (#2046)

* Adjust Readme - Reference PHPStan Level 6

---------

Author: lrljoe

README.md

@@ -5,7 +5,7 @@
 [![Tests](https://github.com/rappasoft/laravel-livewire-tables/actions/workflows/run-tests.yml/badge.svg)](https://github.com/rappasoft/laravel-livewire-tables/actions/workflows/run-tests.yml)
 [![Total Downloads](https://img.shields.io/packagist/dt/rappasoft/laravel-livewire-tables.svg?style=flat-square)](https://packagist.org/packages/rappasoft/laravel-livewire-tables)
 [![codecov](https://codecov.io/gh/rappasoft/laravel-livewire-tables/graph/badge.svg?token=1B9VKO9KWG)](https://codecov.io/gh/rappasoft/laravel-livewire-tables)
-![PHP Stan Level 5](https://img.shields.io/badge/PHPStan-level%205-brightgreen.svg?style=flat)
+![PHP Stan Level 6](https://img.shields.io/badge/PHPStan-level%206-brightgreen.svg?style=flat)
 
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