IBX-9564: ibexa_product_catalog_group_attributes described in Developer Documentation (#2626)

* filter added in dev-doc

* fixes after review

* fix

* example updated

Author: julitafalcondusza

docs/templating/twig_function_reference/product_twig_functions.md

@@ -129,4 +129,21 @@ The `ibexa_is_pim_local` is a helper Twig function that enables changing the beh
         <button type="button">Modify product data</button>
     </div>
 {% endif %}
+```
+
+### `ibexa_product_catalog_group_attributes`
+
+The `ibexa_product_catalog_group_attributes` filter groups product attributes based on the [attribute group]([[= user_doc =]]/pim/work_with_product_attributes/#create-attribute-groups) they belong to.
+
+#### Example
+
+``` html+twig
+{% for group, attributes in product.attributes | ibexa_product_catalog_group_attributes %}
+    <ul>{{ group.name | capitalize }}
+        {% for attribute in attributes %}
+            {% set attribute_definition = attribute.attributeDefinition %}
+            <li>{{ attribute_definition.name }} : {{ attribute | ibexa_format_product_attribute }}</li>
+        {% endfor %}
+    </ul>
+{% endfor %}
 ```