feat: implement addNextQuiz to automate next quiz

[wackerow]

Description

• Removes manual requirement of adding the next property value for the list of Quizzes
• Adds simple util function to add the id of the next item in the array and assign it to the next value; undefined for the final item.

Preview link

https://deploy-preview-13939--ethereumorg.netlify.app/en/quizzes

[netlify[bot]]

✅ Deploy Preview for ethereumorg ready!

Name	Link
🔨 Latest commit	6fee9643cdd76538eac2a40b07a2ece7501b3ed2
🔍 Latest deploy log	https://app.netlify.com/sites/ethereumorg/deploys/673b7e3605828d0008d9065e
😎 Deploy Preview	https://deploy-preview-13939--ethereumorg.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	7 paths audited Performance: 46 (🔴 down 8 from production) Accessibility: 92 (no change from production) Best Practices: 89 (🔴 down 9 from production) SEO: 99 (no change from production) PWA: - View the detailed breakdown and full score reports

---

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