Provided step is ignored in coordinate selection

[observingClouds]

sel_step is not provided to the actual selection:

mllam-data-prep/mllam_data_prep/ops/selection.py

Line 74 in f58cdac

ds = ds.sel({coord: slice(sel_start, sel_end)})

[observingClouds]

Sorry @matschreiner, seems like I have a good 👃 today

[observingClouds]

When addressing #68 it would probably be good to also allow for timedelta types in the range section of the configs