Plotly is not included in the Ribasim Python package

[christianli24]

Please add plotly library to the The Ribasim Python package as this library is used in the irrigation demand tutorial.

[visr]

Since Ribasim doesn't use Plotly itself I don't think we should add it as a dependency. But you raise a good point, we probably should mention explicitly that users need to install Plotly for this tutorial.