Add option to format Jupyter Notebooks in GitHub Action (#3282)

To run the formatter on Jupyter Notebooks, Black must be installed
with an extra dependency (`black[jupyter]`). This commit adds an
optional argument to install Black with this dependency when using the
official GitHub Action [1]. To enable the formatter on Jupyter
Notebooks, just add `jupyter: true` as an argument. Feature requested
at [2].

[1]: https://black.readthedocs.io/en/stable/integrations/github_actions.html
[2]: https://github.com/psf/black/issues/3280



Signed-off-by: Antonio Ossa Guerra <aaossa@uc.cl>