Add live preview functionality to The Source articles

Summary

Add live preview functionality to The Source articles creation process, following the existing implementation used for Blog posts.

Requirements

• Implement live preview for The Source articles in the Decap editing environment
• Allow users to see their changes immediately as they edit
• Provide a button to open the live preview in a new window
• Follow the existing live preview implementation patterns used for Blog posts

Acceptance Criteria

• Live preview displays in the Decap editor for The Source articles
• Changes are reflected immediately in the preview
• "Open in new window" button is available and functional
• Implementation follows existing Blog post live preview patterns
• Preview accurately renders The Source article formatting and styling

Technical Notes

Reference the existing Blog post live preview implementation for consistency and code reuse opportunities.