Add check for article visual content

[davelab6]

Following #4594 I propose a WARN check that (new) families have an ARTICLE page, have a certain minimum lenght (say 100 words or 500 characters), and have at least 1 visual asset embedded in the HTML (and the file(s) are actually present in the repo); the warning message should prompt the user (to prompt the author of the About page, if different) to include an ARTICLE of the required length or more and at least 1 image, preferably an SVG, but can be SVG, PNG, JPEG, MP4 or YouTube link.