Major release with generics support

What's Changed

• Remove dead code by @jeffwidman in #85
• Make NewThreadUnsafeSet() take optional vals. by @jeffwidman in #83
• Delete New*SetFromSlice() and NewSetWith() APIs by @jeffwidman in #84
• feat: improve Add performance by @orisano in #88

New Contributors

• @jeffwidman made their first contribution in #85
• @orisano made their first contribution in #88

Full Changelog: v2.0.0...v2.1.0