Attribute implement ArrayAccess but is not compatible with PHP 8.1

[sugatasei]

ArrayAccess interface is not well implemented for PHP 8.1. Type is missing for methods attributes and return type.

https://www.php.net/manual/en/class.arrayaccess.php

Bug exemples : Return type of Webklex\PHPIMAP\Attribute::offsetGet(mixed $key) should either be compatible with ArrayAccess::offsetGet(mixed $offset): mixed Return type of Webklex\PHPIMAP\Attribute::offsetExists($key) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool PHP Deprecated: Return type of Webklex\PHPIMAP\Attribute::offsetUnset($key) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void