fix(theme-translations): add missing Vietnamese translations

[namnguyenthanhwork]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Test Plan

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

[netlify]

✅ [V2]

Built without sensitive environment variables

Name	Link
🔨 Latest commit	9fa2774
🔍 Latest deploy log	https://app.netlify.com/sites/docusaurus-2/deploys/66ec0c41d810780008688b43
😎 Deploy Preview	https://deploy-preview-10507--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🟠 76	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🟠 58	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 74	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 47	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 72	🟢 100	🟢 100	🟠 86	Report

[slorber]

LGTM but it's probably better if your translations have the same capitalization than the one from the base language (english)

[slorber]

thanks 👍