Add use-case driven examples

[tannerlinsley]

Add three new React examples that focus on common use cases rather than implementation details. Each example defaults to dynamic sizing but includes interactive controls to switch between fixed, variable, and dynamic modes, helping users understand when to use each approach.

• List: Vertical list virtualization with mode switching
• Horizontal List: Horizontal list/carousel virtualization
• Grid: 2D grid virtualization with both row and column virtualization

🎯 Changes

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

[changeset-bot]

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Latest commit: 079cf8f

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