Support MyST in docstrings with `sphinx-autodoc2`

[redeboer]

Need to investigate whether sphinx-autodoc2 is a suitable replacement of sphinx.ext.autodoc, which we currently use. The fact that sphinx-autodoc2 does not perform dynamical analysis could result in differences in the API.

See here fore more info:

• https://myst-parser.readthedocs.io/en/latest/syntax/code_and_apis.html#documenting-whole-apis
• https://sphinx-autodoc2.readthedocs.io/en/latest/quickstart.html#using-markdown-myst-docstrings

See also #61