Incorporate Jupyter notebooks

[annakrystalli]

The current practical content is in Jupyter notebooks. To ensure maximum interoperability and easy interactivity online, it might be best to stick to Jupyter notebooks for the R content too.

hugo_jupyter seems a useful module for this:

• Documentation: https://knowsuchagency.github.io/hugo_jupyter
• Source: https://github.com/knowsuchagency/hugo_jupyter