[IMPROVEMENT] Extend documentation on CalculationMethod

[Thijss]

I would like to be able to make an informed decision on which calculation method to use, without having to consult one of you personally.

The current documentation is a bit short. Would be nice if there was a written comparison between the different methods, and some explanation or examples of use cases.

If you could either add some explanation about the differences or some links t references, that would be nice

[petersalemink95]

Hi @Thijss would you like a small additional explanation next to the table of https://power-grid-model.readthedocs.io/en/latest/user_manual/calculations.html#power-flow-algorithms - or a full in-depth mathematical workout for the various algorithms?

My guess would be the first, but I'd like to double check :)

[Thijss]

Yes, first one would be great 👍