feat: add button group composition fix example

[TEJASWANIANIMIREDDY]

Pull Request Description

Added a standalone demo showcasing button group composition with proper border-radius handling for pill, small, and large button groups. The demo also demonstrates symmetric border rendering between grouped buttons

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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

⚠️ PRs that fail this checklist will be closed without review.

• All changes are inside submissions/examples/button-group-composition-fix/
• Includes demo.html — self-contained, opens in browser with no server
• Includes style.css — raw CSS for the proposed feature
• Includes README.md — what it does, how to use it, why it fits EaseMotion CSS
• No changes to core/
• No changes to components/
• One feature per PR (no bundled unrelated changes)

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Feature Description

What does this add?

A button group composition demo showcasing pill, small, and large grouped buttons.

How does a developer use it?

<div class="button-group pill"> 
   <button>Left</button> 
   <button>Middle</button> 
   <button>Right</button> 
</div>

Why does it fit EaseMotion CSS?

It demonstrates reusable and composable button group patterns while maintaining clean, readable CSS and consistent visual behavior.

Demo

• Demo added (demo.html works by opening directly in a browser)

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Browser Testing

• Chrome
• Firefox
• Edge
• Safari (optional but appreciated)

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Notes for Maintainer

This submission demonstrates proper button group composition for different button shapes and sizes while maintaining symmetric borders and consistent rounded corners.

Fixes #881

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Do not self-merge, even if you have write access.
Maximum 2 active assigned issues per contributor — unassign extras before opening a PR.

[github-actions]

✅ Submission Validation Passed!

Great job! All required files are present.

📁 Folder: submissions/examples/button-group-composition-fix-tejaswani

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!

Thank you for contributing to EaseMotion CSS! 🎉

[TEJASWANIANIMIREDDY]

Hi @SAPTARSHI-coder,

I have submitted a PR for this issue. I added a standalone demo showcasing button group composition with pill, small, and large button groups, along with symmetric border rendering.

PR: #1424

Thank you for reviewing.