Missing notebook documentation for Monte-Carlo

Hi, the documentation repo seems to be missing a notebook explaining the monte-carlo simulation which is currently implemented in pypsa-earth [here](https://github.com/pypsa-meets-earth/pypsa-earth/blob/main/scripts/monte_carlo.py)

I think it would be helpful to have a notebook to explain or describe the Monte-Carlo simulation in the documentation. It can also be used for reference purposes.