Offset with non polar stereographic projections

[mdtanker]

When plotting some map elements, such as a simple basemap, when using a custom EPSG projection, there seems to be a gap or shift.

fig = ptk.basemap(
    simple_basemap=True,
    coast=True,
    region=(
        -11000e3,
        -10000e3,
        10500e3,
        11000e3,
    ),  
    epsg="3857", 
)

fig.show(dpi=200)

[mdtanker]

This appears to be an issue specifically with EPSG 3857 Web Mercator at high latitudes, something to do with using a different ellipsoid than WGS84 or something. I added a warning if users choose this projection.