Rather than rely on template language specific plugins for id attributes, a la this one https://www.npmjs.com/package/markdown-it-anchor we can instead make use of the existing posthtml infrastructure used by the HTML base plugin and the input path to URL plugins to add an id attributes to content.

This then pairs nicely with a web component to add anchors to headings for the UX piece, a la @daviddarnes’ https://github.com/daviddarnes/heading-anchors