Temporary structured pdf of XLSFORM tutorial

Thanks for all the kind words and support. We've been working hard to transfer docs, rewrite docs, and write new docs. We still have a lot of work to do, but it's coming along -- thanks especially to the Outreachy applicants, who have really sped up the work over the last month or so.

I have opened an issue to talk about PDF export. I have some concerns about doing so -- we don't want to encourage the proliferation of outdated documentation -- but it is definitely a possibility. EPUB as well... doable, but I do wonder about the potential problems.

Another docs deployment possibility -- We could add the docs in the Collect app.
This has been discussed briefly here: https://github.com/opendatakit/collect/issues/1398

If we're interested in an offline copy, this would be my highest preference, as we could make sure it updated when people were online with their devices.