0.5.0 was moving in the direction of treating everything like a simple
list. 0.4.3 had some bugs that made complex lists look closer to the
spacing that complex lists use. This resolves both and adds specific
item margins for both cases.
See https://docutils.sourceforge.io/sandbox/html4strict/data/simple-lists.html
The HTML4 writer depended on the `.last` selector, a class added by
Sphinx directly on output. Both writers are not using that method
anymore and instead relying on well supported CSS selectors.
This actually also addresses a number of inconsistencies with margin
spacing in lists. Version 0.4.3 and prior have a number of odd issues
around nested lists that are resolved with this change.
