Token.attr is a dict[str, str | int | float], meta has no restriction on
the value type. attrs is ostensibly meant for html attributes, meta for
any information whatsoever.
previously we did not detect whether lists were supposed to be compact
or not. this will make a difference for manual chapters, so let's stop
not doing that.
headings are not supported in options docs (since it's unclear what that
would be in the final manual, and the docbook stylesheets already have
trouble rendering all docbook constructs correctly). ordered lists
should be supported, but obviously nothing uses them yet.
these modules will be extended with more functionality. md will
ultimately contain MD-related code such as parsers and converter base
classes. docbook will contain renderers.