migrate help.tpo into a gitlab wiki
we are currently using ikiwiki to host our documentation. that has served us well so far: it's available as a static site in the static mirror system and allows all sysadmins to have a static, offsite copy of the documentation when everything is down.
but ikiwiki is showing its age. it's an old program written in Perl, difficult to theme and not very welcoming to new users. for example, it's impossible for a user unfamiliar with git to contribute to the documentation. it also has its own unique Markdown dialect that is not used anywhere else. and while Markdown itself is not standardized and has lots of such dialects, there is /some/ convergence around CommonMark and GFM (GitHub's markdown) as de-facto standards at least, which ikiwiki still has to catchup with. it also has powerful macros which are nice to make complex websites, but do not render in the offline documentation, making us dependent on the rendered copy (as opposed to setting up client-side tools to peruse the documentation).
gitlab wikis, in contrast, have a web interface to edit pages. it doesn't have the macros ikiwiki has, but that's nothing a few commandline hacks can't fix... or at least we should consider it. they don't have macros or any more powerful features that ikiwiki has, but maybe that's exactly what we want.
this is not blocking the trac to gitlab migration, but it would be nice to jump onboard with everyone, since we will be migrating the Trac wiki onto gitlab as well...