doc: update the doc with the new setting for config

docs/add_custom_values.md

@@ -4,7 +4,8 @@
 
 In our example we will add the `short_description` product field to the indexed content.
 
-- [Use event listener to change the product mapping](../dist/src/Search/EventListener/AppendProductMappingSubscriber.php)
+- [Add your elasticsearch config path in `monsieurbiz_sylius_search.elastically_configuration_paths`](../dist/config/packages/monsieurbiz_sylius_search_plugin.yaml#L9)
+- [Extends the product mapping to add the field](../dist/src/Resources/config/elasticsearch/monsieurbiz_product_mapping.yaml)
 - [Add a decorator for ProductMapperConfiguration](../dist/src/Resources/config/services.yaml)
 - [Create DecorateProductMapperConfiguration class](../dist/src/Search/Automapper/DecorateProductMapperConfiguration.php)