As of PHP 8.1, PHP will start throwing deprecation warnings along the lines of:
Deprecated: Return type of [CLASS]::[METHOD]() should either be compatible with [PHP NATIVE INTERFACE]::[METHOD](): [TYPE], or the #[ReturnTypeWillChange] attribute should be used to temporarily suppress the notice
These type of deprecation notices relate to the Return types for internal methods RFC](https://wiki.php.net/rfc/internalmethodreturn_types)) in PHP 8.1.
Basically, as of PHP 8.1, these methods in classes which implement PHP native interfaces are expected to have a return type declared. The return type can be the same as used in PHP itself or a more specific type. This complies with the Liskov principle of covariance, which allows the return type of a child overloaded method to be more specific than that of the parent.
As this package atill has a minimum PHP requirement of PHP 5.6 based on the
composer.json file, the return type (PHP 7.0 feature) can not be added, so I've added the attribute instead.
While attributes are a PHP 8.0 feature only, due to the syntax choice for
#, they will ignored in PHP < 8 and can be safely added.