fix: add missing component stylesheets to packaging manifest

[KRUSHAL2956]

Pull Request Description

Closes #1292. Adds the newer components (chip.css, footer.css, masonry.css, navbar.css, scroll-progress.css, and sidebar.css) to the required assets verification list in scripts/validate-pack.mjs.

This ensures that the npm package dry-run validation will correctly verify the existence of all the component stylesheets in the final release archive, preventing incomplete packages from being released.

---

Type of Change

• ✨ New animation / hover effect
• 🧩 New component
• 📝 Documentation improvement
• 🐛 Bug fix in an existing submission (packaging / build verification checks)
• Other

---

Submission Checklist

⚠️ PRs that fail this checklist will be closed without review.
Note: This checklist is geared towards new community example submissions. Since this is a release/build script validation fix, changes to scripts/ are required.

• All changes are inside submissions/examples/your-feature-name/
• 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)

---

Feature Description

What does this add?

Verifies that new core/component files are correctly captured by npm pack and not accidentally omitted from the release bundle.

---

Notes for Maintainer

Tested and verified locally using node scripts/validate-pack.mjs (successfully validated 20 package files).