Document reasoning for width 100% on children
Document reasoning for width 100% on children

Also add explicit .tutor-ui-horizontal-img rule even
though it's also caught by the [data-type=media].  That way it'll
be explicit that the rule applies to it as well

openstax/tutor-js,openstax/tutor-js,openstax/tutor-js,openstax/tutor-js,openstax/tutor-js