Add a Word .docx option

[jules32]

A note that to make it easier to review and following up from #44, I changed this to a Word output by changing these lines:
https://github.com/Openscapes/series/blob/main/_make_pdf.qmd?plain=1#L8-L14

from pdf to docx on Lines 8 and 14. I just did this locally to produce the .docx but did not push at this point.