minor #13264 Document RenderView method (Midwain)

This PR was merged into the 4.4 branch.

Discussion
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Document RenderView method

Hello!

Current docs doesn't mention renderView() method (Symfony 4.+).
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Commits
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4ae1210 Document RenderView method

Author: javiereguiluz

templates.rst

@@ -446,6 +446,19 @@ the :class:`Twig\\Environment` class::
         }
     }
 
+Rendering a Template's Content
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``renderView()`` method renders a template and returns its content. The content from the template can be used to create a ``Response`` object::
+
+    use Symfony\Component\HttpFoundation\Response;
+    
+    $content = $this->renderView('product/index.html.twig', [
+        'category' => '...',
+        'promotions' => ['...', '...'],
+    );
+    
+    return new Response($content);
+
 Rendering a Template in Emails
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~