Support for input length 16?

[agostbiro]

Hey,

thanks for this awesome library! I saw that in #5 you added support for input length 16, but then decreased it to 13 in #12 presumably to speed up compile time?

I'd need input length 16 for compatibility with https://github.com/iden3/go-iden3-crypto

Would you accept a PR that reintroduces input length 16 behind a feature flag?

Best,
Agost