Possible cobra.io documentation improvements

[JanBenisek]

Documentation improvements to reap:

• Create a GitHub Action such that whenever we push to master, the Sphinx docs files are automatically built and the cobra.io website is recreated
• Would be cool to add the tutorial notebooks to the Sphinx documentation website instead of having them in a folder on the repo (https://stackoverflow.com/questions/38526888/embed-ipython-notebook-in-sphinx-document)