feat: Add first preprocess file

@all here is the first PR, I'll add the slides in main in the close future, if you have to modify something related to preprocessing (for instance change the 'dropna' by a mean/mode initialisation to avoid loosing too much data (here only 158/400 lines have no NaN)) please do it on the feat/preprocessing branch. For anything else, juste create a new branch with feat/your_feat from main. Just don't commit code direclty on main In a recent project, I have seed that another good practice is to rebase the branch to main: a rebase is a type of pull where you sync commits that were behind main (what was modified on main between the moment you created your branch and now) and keep the commits you have ahead (the code you added on your branch that you want to put on main) this way your branch is like Main + my modif when you create a PR, and the commit tree is clear, with only your modifications.