This brings us closer to having a test of mdlintall that's happy -- but
not 100%: there's still errors about checkboxes that look like links and
confuses mdl

Those docs are good, but don't really fit in the Reference section,
they feel like a better fit for the "discussion", until, at least, we
can slot them in the various standard sections in the reference.

We do a pass to comply with Harper's complaints, fix a mdlint warning
and generally try to match our style used elsewhere.

Document new labels regarding blackbox (team#41868)

See merge request !61

The labels that were previously there did not have enough granularity
for cases where we use the blackbox exporter.

The meaning of some of the labels, like `instance` and `alias` was
blurred over time and the information it contains seems to vary in
semantics.

For some alerts, we need to know about the blackbox target as well as
the host that's concerned.

This change to the documentation clarifies that instance only has one
stable semantic and that alias label is always used for containing the
hostname that we as humans would think of when referring to metrics.

To complete the picture, we're adding the `target` label that will
contain the blackbox target, which will untangle the meaning of the
`alias` label.

Closes: nextcloud#30

..but only on the "display". the URL is ok

We keep hitting rate limits, and markdownlint is in debian since
bookworm-backports, so we should be safe.

This is going to be a bit slower as we need to install the package,
but it seems like a minor tweak. If this becomes a problem, we could
make a linter image that ships stuff like mdl and codespell.

service/ci.md: Link and recommend TPA-maintained images

See merge request !60

refs team#41721

refs team#41721

refs team#41721

refs team#41721

It's good to have some meaningful defaults. For the cases of exception
it's nice to know why we decided to stray from the defaults.

I find it easier to read that way, and then it can be used to link
directly to individual years.