feat(docs): Populate Developer Portal with comprehensive documentation framework (#35217)

Co-authored-by: Claude <noreply@anthropic.com>

docs/developer_portal/capabilities/extending-workbench.md

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+---
+title: Extending the Workbench
+sidebar_position: 4
+---
+
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+
+# Extending the Workbench
+
+🚧 **Coming Soon** 🚧
+
+Discover how to extend Superset's main interface and workbench with custom components and functionality.
+
+## Topics to be covered:
+
+- Adding custom menu items and navigation
+- Creating custom dashboard components
+- Extending the SQL Lab interface
+- Adding custom sidebar panels
+- Creating floating panels and modals
+- Integrating with the command palette
+- Custom toolbar buttons and actions
+- Workspace state management
+- Plugin-specific keyboard shortcuts
+- Context menu extensions
+
+## Extension Points
+
+- **Main navigation** - Top-level menu items
+- **Dashboard builder** - Custom components and layouts
+- **SQL Lab** - Query editor extensions
+- **Chart explorer** - Visualization building tools
+- **Settings panels** - Configuration interfaces
+- **Data source explorer** - Database navigation
+
+## UI Integration Patterns
+
+- React component composition
+- Portal-based rendering
+- Event-driven UI updates
+- Responsive layout adaptation
+
+---
+
+*This documentation is under active development. Check back soon for updates!*