feat: add support for additional entry file extensions (mts, cts)

[chenjiahan]

Summary

Add support for additional entry file extensions (mts, cts) and updating the documentation to reflect these changes.

Related links

https://www.typescriptlang.org/docs/handbook/modules/reference.html#module-format-detection

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[netlify]

✅ Deploy Preview for rsbuild ready!

Name	Link
🔨 Latest commit	7053767
🔍 Latest deploy log	https://app.netlify.com/sites/rsbuild/deploys/679107ee4d7a8e0008fece24
😎 Deploy Preview	https://deploy-preview-4415--rsbuild.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 63 (🔴 down 9 from production) Accessibility: 97 (no change from production) Best Practices: 100 (no change from production) SEO: 100 (no change from production) PWA: 60 (no change from production) View the detailed breakdown and full score reports

---

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