Create Jupyter Notebooks as Examples and add them to docs

[maurerle]

See docs on adding jupyter notebooks to readthedocs:

https://docs.readthedocs.io/en/stable/guides/jupyter.html#including-classic-ipynb-notebooks-in-sphinx-documentation

• [ ] RL example "Musterlösung
• [ ] Multi Market example from EIA paper
• [ ] Germany example
• [ ] small simple world script example?

[maurerle]

duplicate of #233