[PropertyInfo] Add ConstructorExtractor documentation

Author: alexandre-daubois

components/property_info.rst

@@ -483,6 +483,36 @@ with the ``property_info`` service in the Symfony Framework::
     // Type information.
     $doctrineExtractor->getTypes($class, $property);
 
+ConstructorExtractor
+~~~~~~~~~~~~~~~~~~~~
+
+The :class:`Symfony\\Component\\PropertyInfo\\Extractor\\ConstructorExtractor`
+tries to extract properties information from the PhpDoc present
+on the constructor, or by using reflection on constructor's arguments::
+
+    // src/Domain/Foo.php
+    class Foo
+    {
+        private $bar;
+
+        public function __construct(string $bar)
+        {
+            $this->bar = $bar;
+        }
+    }
+
+    // Extraction.php
+    use Symfony\Component\PropertyInfo\Extractor\ConstructorExtractor;
+    use App\Domain\Foo;
+
+    $constructorExtractor = new ConstructorExtractor();
+    $constructorExtractor->getTypes(Foo::class, 'bar');
+
+.. versionadded:: 5.2
+
+    The :class:`Symfony\\Component\\PropertyInfo\\Extractor\\ConstructorExtractor`
+    was introduced in Symfony 5.2.
+
 .. _`components-property-information-extractors-creation`:
 
 Creating Your Own Extractors