Update README to mirror new content of config file

Author: miclf

README.md

@@ -97,11 +97,18 @@ This is the contents of the published file:
 return [
 
     /*
-     * The default serializer to be used when performing a transformation.
-     * Leave empty to use the Fractal's default. This can be a string or
-     * it can be an instance of League\Fractal\Serializer\SerializerAbstract
-     */
+    |--------------------------------------------------------------------------
+    | Default Serializer
+    |--------------------------------------------------------------------------
+    |
+    | The default serializer to be used when performing a transformation. It
+    | may be left empty to use Fractal's default one. This can either be a
+    | string or a League\Fractal\Serializer\SerializerAbstract subclass.
+    |
+    */
+
     'default_serializer' => '',
+
 ];
 ```