Create a data cleaning notebook

[joseph-palmer]

[WIP]

TODO

Add in the following data sets

• [x] voting up to 2019
• [x] voting 2021 and 2022
• [x] lyrics
• [ ] Language (own, English, other etc, need to add code.)
• [x] Time since last win
• [x] migration
• [x] border
• [ ] gender (need to add code)

Summary

This PR takes all the cleaning code and puts it in a Jupyter notebook that walks the reader through how the data is sourced and prepared for use in the model. Code and content is taken from the colab notebooks and code uploaded to the cleaning branch which this will merge into.

[KatrionaGoldmann]

Closing without merge since data cleaning was merged elsewhere