- Now putting chapters inside "<article>".
- Doing rendering of context.md + chapter markdown, instead of rendering
  the whole book at once.
- messed about with CSS rendering of headings

This marks the start of the workings: technical notebook project.

This stuff has a long way to go, but I may as well commit it.

Trying to hone in on the idea of indirection, abstraction, generality,
the manipulation of semantics by semantic-agnostic means.