Correct npstereo and spstereo to be polar stereographic projections

[rgrumbine]

in map_tools.py
there are options for npstereo and spstereo, which ordinary readers would take to mean north and south polar stereographic projections, but in the code, it is actually orthographic projection which is used. This is a very different projection.

[aerorahul]

I think the fix is easy enough

self.projection = ccrs.Orthographic(central_longitude=self.cenlon,
                            central_latitude=-90,
                            globe=self.globe)

should be replaced w/

self.projection = crs.SouthPolarStereo(central_longitude=self.cenlon, globe=None)

Similar for North Polar Stereographic projection.

The self.globe attribute could be set based on the selected projection as well

emcpy/src/emcpy/plots/map_tools.py

Line 312 in ba80c32

self.globe = globe