Categorize section types, and highlight optional/required subsections.
Review Request #11692 — Created June 30, 2021 and submitted
This adds some information on the two broad categories of sections:
- Container Sections (those with subsections but no content)
- Content Sections (those with content but no subsections)
The categories link to every section of the given type, and each section
has information identifying its type.
Subsection lists also point out which subsections are optional and which
Built the docs. Checked the new text, made sure all links worked, and
that each section had an identifying type.