In _reproject_raster_to_rhealpix, area_or_point is not written

[rbejar]

For now, I have not found a way to write that tag (search for AREA_OR_POINT in https://gdal.org/user/raster_data_model.html) to the ouput file.
Once this is solved, the function should have a additional argument for the caller to decide if area_or_point will be area or pint.