Add explaination to docs

Author: pmarki

docs/features.md

@@ -24,6 +24,9 @@ Additionally, a PHPStan rule checks that only `Magento\Framework\Data\Collection
 ### ObjectManager type hints
 A type extension is provided so that `Magento\Framework\App\ObjectManager` method calls do return the correct return type.
 
+### ResultFactory type hints
+Correct type is returned from `Magento\Framework\Controller\ResultFactory` based on passed parameter.
+
 ## Magic method calls
 For some classes like `Magento\Framework\DataObject` or `Magento\Framework\Session\SessionManager` PHPStan logic is provided
 to be able to let the magic method calls return proper types.

tests/bitExpert/PHPStan/Magento/Type/ControllerResultFactoryReturnTypeExtensionUnitTest.php

@@ -40,7 +40,7 @@ public function returnTypeDataProvider(): array
     {
         return [
             ['TYPE_JSON', 'Magento\Framework\Controller\Result\Json'],
-            ['TYPE_PAGE', 'Magento\Framework\View\Result\Page'],
+            ['TYPE_PAGE', 'Magento\Framework\View\Result\Page']
         ];
     }