This adds a heavily commented JavaScript example file (frontend_extension.js.example) to the custom_nodes directory. The example demonstrates:
- Extension registration and lifecycle hooks
- Working with node properties including node.imgs
- Adding custom widgets and UI elements
- API communication and WebSocket messaging
- Workflow execution hooks
- Best practices and debugging tips
This addresses issue #3603 by providing developers with a complete, well-documented example similar to the existing example_node.py.example file.
