Feature request: "class" for section-groups

[Jacco-V]

With sections, we can add classes to the section using an key in the json schema:

{% schema %}
{
  "name": "t:sections.example.name",
  "class": "my-section-class",
  "settings": []
}
{% endschema %}

however, with section groups, this is unfortunately not the case. It would be most useful if the "class" key was also supported for the sections groups schema.