docs: add comprehensive usage analytics badges

[ddjain]

📊 Summary

Adds comprehensive usage analytics badges and documentation to help track community adoption.

✨ What's Added

New Badges (8 total):

1. ⭐ GitHub Stars - Community interest & endorsement
2. 🔱 GitHub Forks - Active usage & customization
3. 👁️ GitHub Watchers - Active monitoring
4. 📝 GitHub Issues - Open issues count
5. 🔀 GitHub PRs - Open pull requests count
6. 🔗 Used by - Public repos using this action (dynamic)
7. 📅 Last Commit - Maintenance status
8. 🏷️ Latest Release - Version tracking

New Documentation Section:

• 📊 Usage Analytics section explaining:
  • What each badge measures
  • Why it matters for adoption
  • Note about private repos (2-5x usage multiplier)
  • How GitHub Marketplace analytics work
  • Where insights will be available after publication

🎯 Benefits

✅ Track adoption - See how many repos are using the action
✅ Community engagement - Monitor stars, forks, issues
✅ Maintenance transparency - Show active development
✅ Social proof - Build trust with potential users
✅ Professional appearance - Industry-standard badges

📸 Preview

The badges appear prominently at the top of the README:

• First row: Static project badges (GitHub, License, Coverage)
• Second row: Dynamic usage/analytics badges (Stars, Forks, etc.)

🔍 Technical Details

• All badges use shields.io for consistency
• Social badges (style=social) for stars/forks/watchers
• Dynamic badge for "Used by" count (updates automatically)
• Links to relevant GitHub pages for each metric
• No external analytics services required (pure GitHub API)

📚 Addresses User Request

User asked: "is there any way to have analytics in which we will be able to understand how many time this workflow been called by community?"

This PR provides:

1. ✅ Corrected information about Marketplace insights
2. ✅ Multiple tracking badges showing community adoption
3. ✅ Clear explanation of what can be tracked
4. ✅ Guidance on GitHub's built-in analytics features