Jupyter extension to automatically install with pip

[lucharo]

As of right now the jupyter extension needs to be enabled manually after installing nb2medium via pip:

to install in current conda or virtuale environment:

jupyter nbextension install nb2medium --py --sys-prefix
jupyter nbextension enable nb2medium --py --sys-prefix

And it can be run without --sys-prefix to install system wide.

I know there are ways to have the extension installed, and enabled by default (as jupytext does) but I haven't figured it out.