feat: add skeleton loading animation submission

[AyushPrad2907]

Pull Request Description

This PR adds a new animation submission called Skeleton Loading Animation inside submissions/examples/skeleton-loading-animation/.

The submission introduces a shimmer-based loading placeholder effect that can be used while content is being fetched or rendered. The demo showcases practical use cases including profile cards, article layouts, and dashboard sections.

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Type of Change

• ✨ New animation / hover effect
• 🧩 New component
• 📝 Documentation improvement
• 🐛 Bug fix in an existing submission
• Other (describe below)

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Submission Checklist

• All changes are inside submissions/examples/skeleton-loading-animation/
• Includes demo.html
• Includes style.css
• Includes README.md
• No changes to core/
• No changes to components/
• One feature per PR

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Feature Description

What does this add?

A shimmer-based loading skeleton animation for placeholder content during loading states.

How does a developer use it?

<div class="skeleton"></div>

[github-actions]

✅ Submission Validation Passed!

Great job! All required files are present.

📁 Folder: submissions/examples/skeleton-loading-animation

Files found:

• ✅ demo.html
• ✅ style.css
• ✅ README.md

🚀 Next Steps:

• The maintainer will review your PR
• Respond to any feedback if requested
• Once approved, your contribution will be merged!

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