Make code portable to Windows
Currently, Antora is not portable to Windows. The main issue is paths. Antora does a lot of work with paths and most of the path calculations are incorrect on Windows. Node favors the use of backslashes when resolving and joining paths on Windows. Antora assumes paths contain forward slashes. We'll need to find all the places where backslashes are creeping in and posixify them (esp URLs).
The first goal is to fix that paths so that the test suite works on Windows. Once we get there, then we can see what other issues remain.