[chapter 5] add planetoid example notebook

[amarzullo24]

The implementation of the Planetoid methods (graph regularization) should be added in the report.
You can find it here https://colab.research.google.com/drive/1JDSQy3qPMxpMBd6w17YQRJ1byHMSaa7I?usp=sharing

[deusebio]

Thanks @amarzullo24 ! I will take care of reformatting the Colab notebook and create the associate Poetry environment. I will raise a PR shortly

[deusebio]

It turned out to be a bit harder than I thought. Locally the notebook is extremely slow, but also the unsupervised loss that is produced often goes to infinity. I also tried to run this on Colab, but another issue with the notebook is its memory consumption, which quickly raises above 24 GB on my local (hence then the memory swapping and turning out very slow), but on free-tier Google Colab I only have 12 GB, and it does not even go past the generation of pairs

How did you manage to run the notebook?

[deusebio]

I have nevertheless started to open a PR (#32) without the initial implementation of Planetoid. I have just swapped those cells into a "raw" cell.

[amarzullo24]

That's weird, since I actually run it on Colab (as you can see, the output is still visible in the notebook).
Anyway, let's go on with the PR.