We're changing the subheading name from 'images' to 'illustrations'
so let's update this link, which points to that subheading.

Because I'd confused them previously

Add instructions for how to request help when the html-lint Docker
image is out of date.

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/439130

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/439130

Change from:

OLD: development/documentation/testing.md
NEW: development/documentation/testing/index.md

This allows me to start carving off Vale and Markdownlint info
into separate pages.

- /doc/operations/feature_flags.md
- /doc/development/documentation/styleguide/index.md

Because we recently changed how
it's displayed in the docs.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Because we've recently updated how we do it

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Update format for development docs

Because for now, we're changing the format.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

- Guidance for handling offerings in REST API docs.
- Require periods on full sentences in tables.

Because we're changing how we do it
Because it will be easier to replatform
the docs site this way.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/merge_requests/4517

Fix indentation of lists and table alignment

Two items ("issues" and "merge requests") are pinned by default, but
we want to use the longer way around because it's consistent for all.

Update the links in all docs except user and admin pages