New notebook with step-by-step HydroMT usage

[shartgring]

Version checks

• I have checked that the issue still exists on the latest versions

Kind of issue

Docs are missing

Documentation problem

The 1D, 2D and 1D2D notebooks contain duplicate information and miss some basic HydroMT explanation. It can be considered to streamline the notebooks (merge them and include more step-by-step info) or add an extra introductory notebook. This can be used for DSD 2024 as the starting point for the users of the demonstration