Add styling for the admonition.note

[geographika]

Currently, RST note blocks don't have any formatting (as there is no style applied to the docs):

.. note::

  A complete list of the available objects and properties a Mapfile can have
  can be found in the `MapServer documentation page
  <https://mapserver.org/mapfile/index.html>`_.

This pull request changes the HTML output (for all pages) from plain text:

To a formatted section:

Happy to change the styling, or close this pull request if plain text is preferred. Most Sphinx themes however implement a similar style for .. note::.

Also fix a commented out CSS (// isn't valid).