Arbitrary Base XX support

We should be able to support other alternative base XX alphabets (32, 36, whatever) by allowing some sort of alphabet selection or input, counting the # of characters, and then parsing accordingly.

Cyberchef does some of this today, for a bit of guidance on the UI/UX.

See https://datatracker.ietf.org/doc/html/rfc4648#page-10 for several alphabet definitions that could be preloaded.