docs: add documentation on how to use assets_mode

docs/customization.rst

@@ -69,3 +69,23 @@ Just create a file ``templates/bundles/NelmioApiDocBundle/SwaggerUi/index.html.t
     {% endblock javascripts %}
 
 You can have a look at the `original template <https://github.com/nelmio/NelmioApiDocBundle/blob/master/templates/SwaggerUi/index.html.twig>`_, in ``/templates/SwaggerUi/index.html.twig``, to see which blocks can be overridden.
+
+Assets Loading Options
+-----------------------
+
+The `html_config` settings allow you to configure how assets are loaded for the UI. The `assets_mode` option supports three values: `cdn`, `bundle`, and `offline`.
+
+
+   .. code-block:: yaml
+
+       nelmio_api_doc:
+           html_config:
+               assets_mode: 'cdn' # Other values: 'bundle', 'offline'
+
+`assets_mode`
+~~~~~~~~~~~~~
+
+The three values possible values can be found in `AssetsMode.php <https://github.com/nelmio/NelmioApiDocBundle/blob/master/src/Render/Html/AssetsMode.php>`_
+- **cdn**: Loads assets from `jsDelivr <https://www.jsdelivr.com/>`_.
+- **bundle**: Fetches assets from the bundle in the vendor directory, including updates.
+- **offline**: Loads assets from the local `assets` directory, requiring the developer to update them manually.