improve docs again - Githubissues

[x] embed measurements notebook in docs
[x] clean notebooks/examples (and readme), eg replace netcdf example with ds = df_simple.to_xarray(); ds = ds.assign_attrs(ds_simple.attrs); ds.to_netcdf("file-name.nc") and maybe some variable renaming. Also simplify parallel example so it does not use a nonexising file
[x] add notebooks to docs/pages
[x] increase cli test coverage
[x] fix rwsddl testcase in https://github.com/Deltares/dfm_tools/pull/796
[x] check timezone example code if all still aligns: https://github.com/Deltares/ddlpy/issues/40 (we get "Geen gevevens gevonden" at 11-3-2024, this was not the case before) >> also for ddlpy testbank, this is because ddl is currently being updated and much data was temporarily removed. Wait until it is restored.
[x] change above tests to dummy data, so they will always keep passing also if data is fixed

Deltares / ddlpy