Export Bech32 functions

[10gic]

Exporting the bech32 related functions would increase the utility of this library.

For example, Sui uses bech32 to encode its private keys. https://github.com/sui-foundation/sips/blob/main/sips/sip-15.md

Is your feature request related to a problem? Please describe.
N/A

Describe the solution you'd like
Solution 1:

struct TWBech32;
TWString *_Nonnull TWBech32Encode(TWString* _Nonnull hrp, TWData *_Nonnull data);
TWData* _Nullable TWBech32Decode(TWString* _Nonnull string);  // The hrp part is easy to obtain, it will not be returned

struct TWBech32m;
TWString* _Nullable TWBech32mEncode(TWString* _Nonnull hrp, TWData *_Nonnull data);
TWData* _Nullable TWBech32mDecode(TWString* _Nonnull string);  // The hrp part is easy to obtain, it will not be returned

Describe alternatives you've considered
Solution 2:

enum TWBech32ChecksumVariant {
  TWBech32ChecksumVariantBip173
  TWBech32ChecksumVariantBip350
}

struct TWBech32;
TWString *_Nonnull TWBech32Encode(TWString* _Nonnull hrp, TWData *_Nonnull data, enum TWBech32ChecksumVariant variant);
TWData* _Nullable TWBech32Decode(TWString* _Nonnull string, enum TWBech32ChecksumVariant variant);  // The hrp part is easy to obtain, it will not be returned

Checklist

Resources

Resources link
https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
https://github.com/bitcoin/bips/blob/master/bip-0350.mediawiki

Additional context

Add any other context or screenshots about the feature request here.

[10gic]

Hi @satoshiotomakan, I can work on this. Which solution do you prefer? Do you have any other better solutions?

[satoshiotomakan]

Hi @10gic, good suggestion. I think the Solution 1 seems to be more unambiguous, homogeneous. For example, we have similar TWBase58Encode, TWBase58EncodeNoCheck.

[10gic]

Hi @satoshiotomakan, your comment reminds me that there is one more solution:
Solution 3:

struct TWBech32;
TWString *_Nonnull TWBech32Encode(TWString* _Nonnull hrp, TWData *_Nonnull data);
TWData* _Nullable TWBech32Decode(TWString* _Nonnull string);
TWString *_Nonnull TWBech32EncodeM(TWString* _Nonnull hrp, TWData *_Nonnull data);  // bip350 Variant
TWData* _Nullable TWBech32DecodeM(TWString* _Nonnull string);  // bip350 Variant

It's hard to choose solution 1 and solution 3.

[satoshiotomakan]

Thank you for the PR @10gic, it's merged finally :)