Review how to on adding new fields to the user group management

We need to review the how to on adding new fields to the user group management https://doc.nuxeo.com/nxdoc/how-to-add-new-fields-to-the-user-profile-or-group-profile/

In particular the Display the new field in Web UI section, as we shouldn't need to import the elements and follow the same folder structure we have in Web UI.