Description:

Content for the documentation site (cyrusimap.org) can now be written in
Markdown.  Building the documentation, therefore, will now require myst_parser,
which is what makes this possible.


Documentation:

None needed, really: put a file where you'd put a .rst file, but name it .md,
and it will be processed.  This uses myst:
https://github.com/executablebooks/MyST-Parser


Config changes:

n/a


Upgrade instructions:

n/a


GitHub issue:

n/a
