enh: enabled PDOS to return an xarray.DataArray object
enh: enabled PDOS to return an xarray.DataArray object

The xarray dataarray is extremely useful because it retains
N-D data with specific coordinates.

TODO add documentation on how to calculate sums of PDOS.

Signed-off-by: Nick Papior <81a73bca3d342ffee33d7cf845fdbf77b6553831@gmail.com>

zerothi/sisl,zerothi/sisl