Added sphinx_copybutton, updates to docs

[Euquimides]

Hi! Regarding the ticket #219, I added the following:

1. Noticed some dependencies missing when building the documentation. Since matplotlib.sphinxext.plot_directive is in conf.py I added pip install matplotlib. Also, it asked for pydata_sphinx_theme.
2. Indicated a possible solution when building the .rst files in Windows Powershell.
3. Added sphinx_copybutton as indicated in the ticket above.

I builded and it seems to be working now for the docs:

I stay attentive to any issues noticed in this PR. Thanks!

[rsokl]

Thanks! The copybutton extension needs to be included in docs/requirements.txt

[Euquimides]

Hi @rsokl ! I added the extension to docs/requirements.txt. I built the docs again in a new environments and it seems to be working fine.