0.21.0

What's Changed

New Features 🚀

• implement value collection for controlled vocabularies by @wow-such-code in #25
• Feature/use header enums by @wow-such-code in #27

Others 🧃

• inform user about unknown mhc class instead of throwing exception by @wow-such-code in #24

Full Changelog: 0.20.3...0.21.0