FEAT: Improve note support to include embedded directives (such as code)

[mmcky]

The current solution for note support is to transfer the contents of note in the text format through to the notebook as a block quote titled with Note. It might be nice to support embedded directives such as code blocks

Current test: code_blocks.rst contains an example that can be improved upon

.. NOTE::

   A code block in a note::

       >>> 1+1

   Another one::

       >>> 1+1

See PR #81

[mmcky]

• construct a test case in tests/