Update areas.rst (#1983)

* Update areas.rst

'with_annotations' option is not mentioned in actual documentation

* Slight changes

* Rephrase

Resources/doc/areas.rst

@@ -32,6 +32,7 @@ You can define areas which will each generates a different documentation:
             store:
                 # Includes routes with names containing 'store'
                 name_patterns: [ store ]
+            
 
 Your main documentation is under the ``default`` area. It's the one shown when accessing ``/api/doc``.
 
@@ -52,3 +53,38 @@ Then update your routing to be able to access your different documentations:
     #    defaults: { _controller: nelmio_api_doc.controller.swagger }
 
 That's all! You can now access ``/api/doc/internal``, ``/api/doc/commercial`` and ``/api/doc/store``.
+
+Use annotations to filter documented routes in each area
+--------------------------------------------------------
+
+You can use the `@Areas` annotation inside your controllers to define your routes' areas.
+
+First, you need to define which areas will use the`@Areas` annotations to filter 
+the routes that should be documented:
+
+.. code-block:: yaml
+
+    nelmio_api_doc:
+        areas:
+            default:
+                path_patterns: [ ^/api ]
+            internal:
+                with_annotations: true
+                
+Then add the annotation before your controller or action::
+
+    use Nelmio\Annotations as Nelmio;
+
+    /**
+     * @Nelmio\Areas({"internal"}) => All actions in this controller are documented under the 'internal' area
+     */
+    class MyController
+    {
+        /**
+         * @Nelmio\Areas({"internal"}) => This action is documented under the 'internal' area
+         */
+        public function index()
+        {
+           ...
+        }
+    }