docs: Add TOC requirement
State that all documents should contain a table of contents.
Partially fixes:
@@ -17,6 +17,8 @@ All documents must:
- Be written in [GitHub Flavored Markdown](https://github.github.com/gfm) format.
- Have a `.md` file extension.
+- Include a TOC (table of contents) at the top of the document with links to
+ all heading sections.
# Notes
