Port toWords

[REASY]

Port toWords (https://github.com/bitcoinjs/bech32/blob/605655d6b37a782345549cd1388db688a96ad56f/src/index.ts#L79) would be very useful to fully move to one library.

I can create PR if needed.

[danpape]

Thanks Artavazd--if you have a PR ready, please submit it and I will take a look.