* Extend table of contents to show subheadings and include a script to
  automatically parse the TOC from the HTML rendered file.
* Rewrite the first paragraphs to give a short but sufficient
  introduction, which removes the need for a separate introduction
  section.
* Rewrite the first actual section to summarize the benefits, and
  simplify the first most important sections to be easier and shorter to
  read.
* Add examples to real use of Salsa CI.
* Update section about the Salsa CI team, and add a section about Salsa
  Admins and general Debian documentation at the end.
* Explain how to run Salsa CI from an existing .gitlab-ci.yml file and
  how to not run it on every commit.

[ci skip]