python-codex32 reference impl

[BenWestgate]

apoelstra/rust-codex32#2 (comment):

@BenWestgate if you have a rewrite feel free to open a PR -- if it's not too hard to review I'm happy to take it in.

But I think the correct direction to rewrite in is one where we add a rust-bech32 dependency, use that for all the checksumming and encoding stuff, and then here we add (a) utility methods, and (b) constructors and accessors for the id/threshold/share index.

I have wrote this python implementation that covers more tests than the rust one does. It also does the approach above and relies on general checksum and bech32 modules. So it also passes Bech32/Bech32m tests.

It includes new test vectors for bitcoin/bips#2040 and bitcoin/bips#2077.

From: https://github.com/BenWestgate/python-codex32

Published on PyPI: https://pypi.org/project/codex32/