Floodplain 1D schematization

[JoostBuitink]

Add support for 1D floodplain schematization, to allow the river to

To add in Wflow.jl:

• interpolate between (user-defined) relation between flood depth and floodplain width. Data will be provided in the staticmaps.nc, with a dimension defining fixed intervals of flood depth (e.g. 1 m), with values of floodplain width for each river pixel (likely averaged per river branch, see hydromt_wflow issue).
• update roughness according to the flood extent of that timestep

See also the issue in hydromt_wflow: https://github.com/Deltares/hydromt_wflow/issues/107