Update H7 checker to look for and flag Aria-tagged H7s

[admoorgit]

The H7 checker will display H7s that are present in a NOFO on import. It does not flag H7s that are created using the "div role" method, which is:

content

Ideally, NOFO producers will create new sections when headings aren't tagged on import. This doesn't always happen (due to deadlines, familiarity with the tool, etc), as designers will often tag headings within an existing subsection and not create a new section for it.

If this is done with an H7, there is a chance the designer will miss tagging it when preparing the final PDF since it is not flagged by the H7 checker.

Is there a simple check we can perform to include all of these outliers?

This is very low priority, as it is rare. It may also be addressed with a docraptor update.

[pcraig3]

This is closed since #204 went in.