Raise minimal PHP version to 8.1

PR Summary

This pull request includes numerous changes aimed at improving the project. Here's a breakdown of what has been done.

GitHub Pull Request Template Added A template for pull requests has been included which makes creating future requests standardized and more streamlined.
Changes to Github Workflows for Push and Pull Requests We have updated several GitHub workflow files. Specifically, we've updated the file event configurations with modifications focusing on the 'branches' and 'paths-ignore' sections. Essentially, these changes help refine the triggers for our automated tasks, ensuring they run at the right time and in the right situations.
Update to PHP requirement The PHP requirement in the composer.json file has been updated. Our project now requires at least version 8.1 (up from previously 8.0) to ensure we can take advantage of the latest features.
Updated Dependencies We have also updated several dependencies in the composer.json file. These include updated versions for phpunit, rector, and psalm, which are tools we use to ensure our code is working correctly.
Changes to psalm.xml File The psalm.xml file has been updated. This includes a change in the error level along with adding more specific error rules. This allows our code validation to be more rigorous and nuanced.
Updates to rector.php File A new class was added to be skipped during the process in the rector.php file, and the level set was updated. This helps refine how our project is evaluated for potential improvements.