Use new video player include - Use consistent VTT naming

[remibetin]

Simplify VTT translations management (context in https://github.com/w3c/wai-translations/issues/117)

🚩Dependencies

• Merge https://github.com/w3c/wai-website-data/pull/113 before this PR
• Merge https://github.com/w3c/wai-website/pull/377/ before this PR
• Merge https://github.com/w3c/wai-website-theme/pull/67 before this PR

[netlify[bot]]

✅ Deploy Preview for wai-eval-overview ready!

Name	Link
🔨 Latest commit
🔍 Latest deploy log	https://app.netlify.com/sites/wai-eval-overview/deploys/656626b7b8c495195baad93e
😎 Deploy Preview	https://deploy-preview-63--wai-eval-overview.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.