Refactor to simpler JS

[coolaj86]

This is in preparation for a larger refactor to update to modern, cross-platform async WebCrypto, Uint8Array, nobleSecp256k1, etc.

• make Prettier
• pass stricter lint rules
• use UMD-ish exports
• remove prototypes (in favor of plain object)
• remove defineProperty getter/setter (in favor of plain getXyz()s)
• remove assert
• remove safe-buffer
• updated mocha tests
• added Types 🎉
• Changed a few assert(x, msg) to if (!x) { throw new Error(msg) } to satisfy tscs style of nullish checking.

I actually meant to PR this onto my own fork, but... I think it could serve well here too for a v3.

The individual commits are very atomic as to be easy to read and reason about.