add docs

[visr]

I plan to use Quarto, similar to https://github.com/Deltares/Ribasim. With this we can easily include notebooks into our documentation as well. Some points for our developer docs:

          Some things noticed:

• Win-users (expect the majority in our community) need to use powershell in the pixi install instructions: https://deltares.github.io/Ribasim/contribute/python.html#setting-up-pixi. Something Google tells you immediately, but nevertheless most will default try in CMD and fail.
• pixi run install is something we need to add in the docs
• pixi run python is something we need to add in the docs as well

Other than that, works like a charm!

Originally posted by @d2hydro in #17 (review)

[visr]

Closed as a duplicate of #13