Revise notebooks

[MartinSpindler]

For the polishing of the notebooks, a list of the notebooks is here:

https://docs.google.com/spreadsheets/d/1RL01oaOYDZ2PM9CtjOShPM_dOrxbFbnd72dHPMOpPds/edit?usp=sharing
and the notebooks sections in the book (might slightly differ).

Tasks:

1. Checking all notebooks (chapter by chapter)
   a) if they run without error and are correct, in particular

• compare results with the results in the book
• compare results between R and Python versions
• for long computations in the notebooks raise note
• sufficient documentation of the notebooks
  b) they should all be stored at github
  https://github.com/CausalAIBook/MetricsMLNotebooks
  c) For b) translation of kaggle scripts (R) to Jupyter notebooks for use colab
  script: https://github.com/CausalAIBook/MetricsMLNotebooks/blob/main/Rmd2ipynb
  d) Updating the entries and links in the google table above; adding missing notebooks

2. If missing, translation of notebooks from R to Python or the other way around, so that R and Python scripts are available (but might differ)
3. Preparation of new notebooks (Oliver is working on DiD; RD next)