Is your feature request related to a problem? Please describe.
This issue is coming out of a discussion on post https://dev.to/s_aitchison/getting-heading-levels-right-including-here-on-dev-439
A substantial proportion of posts on DEV break WCAG guidance on heading levels. The post title automatically becomes the
h1 of the page; from that point on heading levels should only increase by 1.
What you actually see in reality is a lot of additional
h1 elements, and then quite often non-sequential heading levels beyond that.
It would be a boost for accessibility if we could help limit or prevent this in some way. As a bit of context, the latest WebAIM screen reader user survey indicated that close to 70% of users prefer to navigate by heading level, and the ability to scan content this way is compromised by non-WCAG compliant heading usage.
Describe the solution you'd like
When viewing a post in 'preview' mode, it would be good to see heading level issues flagged in the "Heads up" warning that appears at the top of the page. At a minimum, flagging duplicate
h1s, but ideally linting for other issues in the heading levels (e.g. an
h3 being present but no