add Vietnamese language

[hckhanh]

Closes

✅ Pull Request Checklist:

• [ ] Included link to corresponding React Spectrum GitHub Issue.
• [ ] Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• [ ] Filled out test instructions.
• [ ] Updated documentation (if it already exists for this component).
• [ ] Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

🧢 Your Project:

[snowystinger]

Thanks so much for this. Really cool. We'll need to discuss some strategy on our end, probably in the new year. Just want to set expectations. We'll need to figure out how to best support new languages being added. In the meantime, you may want to use patch-package https://www.npmjs.com/package/patch-package to get the support you need, since I assume these are not strings we expose for you to pass in on your own?

[snowystinger]

Direction we're considering heading for different locale support https://github.com/adobe/react-spectrum/discussions/2999#discussioncomment-2697600

[snowystinger]

Closing until we have a better idea of how to handle this