Group module attributes/constants in separate summary table

[sammorley-short]

Currently documented module constants/attributes are listed with their values, but there is no summary table displayed. It would be great if a summary table could be added to these.

I believe this is because these constants/attributes exist in visible_children here, but there is no associated summary table generated by the template. I couldn't work out exactly how module attributes are identified and classified under the hood, but if they are, then it seems like one could simply define visible_attributes by filtering from visible_children and then adding the following section to the template:

{% block functions scoped %}
{% if visible_attributes %}
Attributes
~~~~~~~~~

.. autoapisummary::

{% for attribute in visible_attributes %}
   {{ attribute.id }}
{% endfor %}


{% endif %}
{% endblock %}

If that diagnosis and solution is correct, then I could take a pass at implementing this and submit it via a PR. But since I am unfamiliar with what's going on under the hood here I am unsure if this would actually work.

P.s. great package btw. Thanks for all the hard work 👌 👌 👌