`sphinx.ext.apidoc` emits reStructuredText by default, which is the last thing in the build producing rst. Point it at Markdown templates and generate the pages with a `.md` suffix. The `automodule` calls stay inside `eval-rst` fences so the Python docstrings, which are written in rst, keep being parsed as rst. The marionette docstrings relied on named hyperlink targets, whose definitions do not resolve across an `eval-rst` boundary; use embedded URIs instead. Also update the links pointing at the generated `marionette_driver` page. Differential Revision: https://phabricator.services.mozilla.com/D321834