Currently, some documentations are written in Markdown while some are in ReStructuredText. I think it's better to use a consistent format so that new contributors won't be confused.
$ find . -name '*.rst'
./README.rst
./doc/install.rst
./doc/overview.rst
./doc/index.rst
./doc/api/index.rst
./doc/_templates/autosummary/module.rst
./doc/_templates/autosummary/class.rst
./doc/_templates/autosummary/exception.rst
./doc/_templates/autosummary/method.rst
./doc/_templates/autosummary/base.rst
./doc/_templates/autosummary/function.rst