Note the upstream refactor from mkdocs-simple v1 -> v2 was fairly large, so
this is a rather larger update than most. And in fact one feature of
mkdocs-semiliterate (universal markdown extraction) was incorporated into
mkdocs-simple, so the initialization of this plugin is noticeably simplified
as a result.
Also updates mkdocs to 1.4.
Also syncs somewhat better with the latest release of mkdocs-simple-plugin
and corrects some typos.
Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #19
