Add TELEMAC support

[pmav99]

TELEMAC is using its own output format called serafin or selafin. There is a GDAL driver for this format, but AFAIK there is no out-of-the-box way of opening them with xarray.

Since we would like to be able to support TELEMAC in thalassa, we should investigate:

1. if it is possible to open SELAFIN files using xarray
2. Failing that, if it is possible to convert SELAFIN files to something that xarray can handle (e.g. netcdf).

As soon as we have the data in xarray we can add a "normalization" function: https://github.com/ec-jrc/Thalassa/blob/master/thalassa/normalization.py

There is a relatively long issue discussing something similar here. I only skimmed through it but we might find something useful there.

[pmav99]

For the record, even though TELEMAC does have a Python API, since AFAIK there is no really easy way to install it (i.e. pip/conda), I think I would prefer not having a script that uses TELEMAC's python API in thalassa.

If we end up converting SERAFIN to a different format, which I suspect we might have to, I think that such a script should exist as a standalone tool and the idea is that this script should be used as an intermediate post-processing step before visualizing the data with Thalassa