feat: change to async based api

[tplooker]

Description

Migrates to an asynchronous based api to maintain an interoperable public interface with other bbs-signature libraries in the TS/JS ecosystem

• [x] Tests for the changes have been added (for bug fixes / features)
• [x] The commit message(s) follow conventional commits
• [ ] Documentation has been added / updated (for bug fixes / features)
• [ ] Changes follow the contributing document.

Motivation and Context

As alluded to in the description in order for TS/JS based bbs-signature libraries to have a common public interface we are shifting this API towards a promise based API.

Does this PR introduce a breaking change?

• [x] Yes
• [ ] No

All API's now return a promise wrapped result

Which merge strategy will you use?

• [x] Squash
• [ ] Rebase (REVIEW COMMITS)

[github-actions[bot]]

Total Coverage: 87.60%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
src
bbsSignature.ts	100%	75%	79.73%	150, 175, 230, 232, 233, 234, 235, 242, 253, 254, 271, 272, 273, 274, 282
bls12381.ts	83.33%	100%	100%	31, 46, 61, 76
bls12381toBbs.ts	100%	100%	100%
index.ts	100%	100%	100%
src/types
BlsKeyPair.ts	100%	100%	100%
index.ts	100%	100%	100%

[github-actions[bot]]

Total Coverage: 87.60%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
src
bbsSignature.ts	100%	75%	79.73%	150, 175, 230, 232, 233, 234, 235, 242, 253, 254, 271, 272, 273, 274, 282
bls12381.ts	83.33%	100%	100%	31, 46, 61, 76
bls12381toBbs.ts	100%	100%	100%
index.ts	100%	100%	100%
src/types
BlsKeyPair.ts	100%	100%	100%
index.ts	100%	100%	100%

[github-actions[bot]]

Total Coverage: 87.60%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
src
bbsSignature.ts	100%	75%	79.73%	150, 175, 230, 232, 233, 234, 235, 242, 253, 254, 271, 272, 273, 274, 282
bls12381.ts	83.33%	100%	100%	31, 46, 61, 76
bls12381toBbs.ts	100%	100%	100%
index.ts	100%	100%	100%
src/types
BlsKeyPair.ts	100%	100%	100%
index.ts	100%	100%	100%

[github-actions[bot]]

Total Coverage: 87.60%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
src
bbsSignature.ts	100%	75%	79.73%	150, 175, 230, 232, 233, 234, 235, 242, 253, 254, 271, 272, 273, 274, 282
bls12381.ts	83.33%	100%	100%	31, 46, 61, 76
bls12381toBbs.ts	100%	100%	100%
index.ts	100%	100%	100%
src/types
BlsKeyPair.ts	100%	100%	100%
index.ts	100%	100%	100%

[github-actions[bot]]

Total Coverage: 87.60%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
src
bbsSignature.ts	100%	75%	79.73%	150, 175, 230, 232, 233, 234, 235, 242, 253, 254, 271, 272, 273, 274, 282
bls12381.ts	83.33%	100%	100%	31, 46, 61, 76
bls12381toBbs.ts	100%	100%	100%
index.ts	100%	100%	100%
src/types
BlsKeyPair.ts	100%	100%	100%
index.ts	100%	100%	100%

[kdenhartog]

@tplooker I think this is ready to go. Anything else we need to do to merge it?