shapely fix + license

[esoteric-ephemera]

• Close Plotting issue via get_convex_hull_and_centroid for simple alloy systems #1 by using shapely.convex_hull.boundary instead of shape.convex_hull.exterior (dropped in shapely>=2.0 seemingly)
• Close Missing license file #10 by adding an appropriate BSD license

Note that the AlloySystem.get_convex_hull_and_centroid method will still fail if an alloy system doesn't have a realistic convex hull for a material:

from mp_api.client import MPRester
from pymatgen.analysis.alloys.core import AlloySystem

with MPRester() as mpr:
  a = mpr.materials.alloys.search(material_ids=["mp-19835"])

asys = AlloySystem(ids = {getattr(d.alloy_pair,k) for d in a for k in ('id_a','id_b')}, alloy_pairs = [d.alloy_pair for d in a])
print(asys.get_convex_hull_and_centroid())
>>> NotImplementedError: Sub-geometries may have coordinate sequences, but multi-part geometries do not

The reason for this being that the data going into the convex hull is the cube root of cell volume against band gap, but all of the entries in this system are metals. Thus the convex hull is a flat line at zero band gap for any input volume, and shapely can't find an appropriate boundary

[tschaume]

Thanks @esoteric-ephemera! Looks good. I updated the github actions to run tests with the latest dependencies. Would you mind seeing if you can resolve the mypy errors in the linting action? Thanks!

[esoteric-ephemera]

Yep on it!