PHP 8.1 deprecated notice

[fundament83]

The following deprecated notices were found while using the phpstan tool:

src/QueryPath/CSS/Selector.php
line 61: Return type mixed of method QueryPath\CSS\Selector::getIterator() is not covariant with tentative return type Traversable of method IteratorAggregate::getIterator()
line 76: Return type mixed of method QueryPath\CSS\Selector::count() is not covariant with tentative return type int of method Countable::count()

src/QueryPath/DOMQuery.php
line 367: Return type mixed of method QueryPath\DOMQuery::count() is not covariant with tentative return type int of method Countable::count()
line 3988: Return type mixed of method QueryPath\DOMQuery::getIterator() is not covariant with tentative return type Traversable of method IteratorAggregate::getIterator()

src/QueryPath/QueryPathIterator.php
line 22: Return type mixed of method QueryPath\QueryPathIterator::current() is not covariant with tentative return type mixed of method Iterator::current()