fix: add spinner animation to ease-btn-loading

[Muskankr]

Pull Request Description

This PR fixes Issue #36515 by adding a visible spinner animation to the ease-btn-loading state.
The loading button now shows a rotating spinner, making the state visually clear.

---

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/btn-loading-spinner/
• Includes demo.html
• Includes style.css
• Includes README.md
• No changes to core/ or components/
• One feature per PR

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Feature Description

What does this add?
Adds a spinner animation to the ease-btn-loading state.

How does a developer use it?

<button class="ease-btn ease-btn-primary ease-btn-loading">
  <span class="spinner"></span>
  Loading...
</button>


Thanks for reviewing my PR!

[SAPTARSHI-coder]

✅ Submission Validation Passed!

Great job! All required files are present and valid.

📁 Folder: submissions/docs/ease-btn-loading

Files found:

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

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

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[github-actions]

🎉 Congratulations on your PR merge, @Muskankr! 🚀

Thank you so much for your valuable contribution to EaseMotion CSS! Your code is now merged into the main branch.

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[github-actions]

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