Add interactive timeline visualization with three visual eras

[AlexU-A]

Summary

• Adds a complete HTML/CSS/JS timeline visualization for Drupal history
• Three distinct visual eras aligned with major Drupal versions:
  • Retro (up to 2007): Windows 95/early web style for Drupal 1–5
  • Growth (2008–2014): Classic Drupal blue theme for Drupal 6 & 7
  • Modern (2015+): New Drupal brand identity for Drupal 8+
• Scroll-triggered animations using Intersection Observer
• Floating year indicator that changes style per era
• Progress bar showing scroll position
• Each era has its own header banner
• Footer with credits linking to this repo, DrupalHistory.org, and contributors
• Uses official Drupal brand assets (renamed to remove spaces for GitHub Pages compatibility)
• Noto Sans typography (official Drupal font)

Test plan

• Open index.html via local server (python3 -m http.server)
• Scroll through timeline and verify three eras display correctly
• Check scroll animations trigger as items come into view
• Verify floating year indicator appears and changes style per era
• Test filter buttons work correctly
• Check mobile responsiveness
• Deploy to GitHub Pages and verify assets load correctly

🤖 Generated with Claude Code

[AlexU-A]

Hayo, I thought we needed to add some different

Incidentally, the designs were assisted by the Drupal Brand Skill I created: https://github.com/zivtech/drupal-brand-skill

You can see this live at: https://zivtech.github.io/drupal-timeline-viz/