the path to the mirror settings have changed, and mention the caveat
about the homepage. alo filed an issue to improve *that*.

There's currently 176 spelling errors in the wiki, and there were some
in this very file (`service/documentation.md`), but I've fixed those
so CI passes here.

This also required (I think) renaming the `test` job to `mdlint`
otherwise we would be somewhat incoherent: the spell check job is also
a "test" job...

This one could be interesting in the context of the multiple wikis
scenario, where they could all aggregate in a single site. But alas,
it only supports asciidoc.

i actually redid the mirror procedure with this setting enabled to see
if this commit will overwrite a test commit I just did on the wiki,
let's see...