Add PHP-8.1 and PHP-8.2 tests in GitHub action

[peter279k]

Changed log

• Add PHP-8.1 and PHP-8.2 tests in the GitHub workflow action.
• Apply coding style fix via the PHP-CS-Fixer.
• Remove the ignored '#Cannot cast mixed to string.#' error setting to avoid following error message:

$ php ~/composer.phar phpstan
> phpstan analyse -c phpstan.neon --no-progress --ansi
 -- ------------------------------------------------------------------------------------------
     Error
 -- ------------------------------------------------------------------------------------------
     Ignored error pattern #Cannot cast mixed to string.# was not matched in reported errors.
 -- ------------------------------------------------------------------------------------------



 [ERROR] Found 1 error