feat: add Timeline component

[PrtHub]

Description

This PR adds a new Timeline component to the UI library. The Timeline component is designed for displaying chronological events or activities in a vertical layout.

Features

• Vertical timeline layout with dots and connectors
• Support for multiple dot variants (default, success, error, warning)
• Customizable content sections
• Responsive design
• Accessible structure
• Support for both default and new-york themes

Added Files

• apps/www/registry/default/ui/timeline.tsx
• apps/www/registry/new-york/ui/timeline.tsx
• apps/www/registry/default/example/timeline-demo.tsx
• apps/www/registry/new-york/example/timeline-demo.tsx
• apps/www/content/docs/components/timeline.mdx

Screenshots

Checklist

• Component follows Shadcn UI design patterns
• Implemented in both default and new-york themes
• Added comprehensive documentation
• Added example usage
• Tested for accessibility
• Follows project's coding style

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