feat: Use firstPublishedAt as the blogpost date

[lsarni]

Ticket: GWW-83

Main features

• Use firstPublishedAt instead of createdAt as the date shown on the blogposts.
• Sort the blogposts by firstPublishedAt

[netlify[bot]]

✅ Deploy Preview for global-water-watch-website ready!

Name	Link
🔨 Latest commit	266e8c91afe338a4baddf826467d46714c30557b
🔍 Latest deploy log	https://app.netlify.com/sites/global-water-watch-website/deploys/6398492aba23900009e10ba3
😎 Deploy Preview	https://deploy-preview-179--global-water-watch-website.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 settings.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication