Instruct cs-fixer to declare nullable parameter types explicitly

Implicit nullable parameter types are deprecated in PHP 8.4

.php-cs-fixer.php

@@ -17,6 +17,7 @@
         'native_function_invocation' => ['include' => ['@all']],
         'final_class' => true,
         'php_unit_mock_short_will_return' => true,
+        'nullable_type_declaration_for_default_null_value' => true,
     ])
     ->setFinder($finder)
 ;