Update PHP version to 8.1 and see how Slic runs

[sc0ttkclark]

Testing Slic with PHP 8.1

[what-the-diff]

PR Summary

• 🚀 PHP version upgrade
  Upgraded the PHP version from 7.4 to 8.1 for improved performance and added features.
• 🔧 Composer install optimization
  Composer install now uses the --no-dev flag, making it faster and more efficient by only installing necessary dependencies.

[what-the-diff]

PR Summary

• 🧹 Removed PHP version configuration
  Simplified setup by removing the need to configure PHP version manually

• 🌐 Added new environment variable for PHP version
  Easier way to set the PHP version by using an environment variable

• 🚀 Changed composer install command
  Reduced dependencies by skipping dev dependencies during install

[what-the-diff]

PR Summary

• 🚀 Upgrade to PHP 8.1
  The PHP version has been updated to 8.1 in the project.
• 🧹 Simplified testing setup
  We've simplified the testing configuration file, making it easier to maintain.
• 🔄 SLIC integration
  SLIC now handles setting up the PHP environment using the specified version.