Support code-block ':caption:' options

[ocket8888]

What's the problem this feature will solve?
A lot of Python projects use Sphinx for documentation, which allows a caption option to its code-block directive. That, obviously, lets people provide captions for their code-blocks. But the renderer used by PyPI doesn't support that option.

Describe the solution you'd like
I'd like PyPI to support captions on their code-blocks, so that I don't have to push built packages that use a different version of the README than is actually checked into source control.

Additional context
Example:

.. code-block:: shell
            :caption: A Caption

            echo "Some actual code"

Should render like e.g.:

A Caption

echo "Some actual code"

[miketheman]

See https://sourceforge.net/p/docutils/feature-requests/62/ for docutils support