Nouveau wiki migration

[Karol Herbst]

Hi everybody,

I think it's time to finally move our wiki from the old infrastructure
over to gitlab pages.

This comes with several benefits:
* full control through git over the ikiwiki pipeline (setup files,
plugins, system packages, ...)
* random users are able to create MRs against the wiki as long as they
are willing to create a gitlab account.
* possible to migrate over to a different wiki generator or mix and
match or whatever.
* no CGI stuff on the wiki as we don't use ikiwiki for the git
operations anymore

To view the migrate wiki visit this URL:
https://nouveau.pages.freedesktop.org/wiki/
the gitlab project lives here: https://gitlab.freedesktop.org/nouveau/wiki

There are a couple of changes I already made:
* convert the perl ikiwiki setup file to yaml:
https://gitlab.freedesktop.org/nouveau/wiki/-/blob/master/nouveau.yml
* reworked the setup file to throw out unused plugins and adjust
settings for gitlab
* enabled HTML5 (does change the style slightly, but also fixed some
regressions)
* pulled in external sources (from the fdo.org server)
* moved mdwn files into their own subdirectory

For now I changed everything inside one big commit:
https://gitlab.freedesktop.org/nouveau/wiki/-/commit/6f2d1669884af186863718ad827f65372a0c5c43

There are a couple of remaining issues/questions:
* the gitlab CI pipeline fails quite a bit, which could be annoying
* there is a delay between editing and changes going live (usually
below a minute though)
* should we disallow direct editing of files for project members so we
could CI the changes are still valid?

Next steps:
* verify everything still works
* fix remaining issues
* final step: point the subdomain to the new gitlab pages URL

If anybody else is interested in moving their wikis over, don't
hesitate to ask me questions or just copy whatever I did :)