Start using semantic markup (#6627)
* Start using semantic markup.
* Forgot some places.
* Fix typo.
* Use 'ignore:' prefix until https://github.com/ansible-community/antsibull-docs/pull/155 is out.
* Break too long line.
(cherry picked from commit 011b2f8bdc)
Co-authored-by: Felix Fontein <felix@fontein.de>