Export VineNativeEnum class

[simoneNEMO]

🔗 Linked issue

Fixes issue #59

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The schema class VineNativeEnum is not currently exported while all other schema classes are causing an error by the Typescript compiler. This PR simply adds an export for such class.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[thetutlage]

Thanks 👍