Update "What are extensions?"
Under https://extensions.typo3.org/about-extension-repository/what-are-extensions/ it's written:
Documentation: Extensions can easily be well-documented since a very flexible and powerful integration of OpenOffice Writer documents (sxw) has been deployed. It really can't be easier.
Since some years we do use reStructuredText instead of sxw. Also we want to get rid of sxw support in the future.
Maybe change to something like:
Documentation: Extensions can easily be well-documented since a very flexible and powerful integration of reStructuredText and Sphinx has been deployed. It really can't be easier.
We might link reStructuredText to http://www.sphinx-doc.org/en/master/usage/restructuredtext/index.html And Sphinx to http://www.sphinx-doc.org/en/master/index.html (I've to check the correct version for the link, or we might link always to master.