Add information on instantiating EventChain directly

[masenf]

[greptile-apps]

Greptile Summary

This PR adds documentation to the "Wrapping React Components" section that explains how to directly instantiate EventChain objects when integrating React libraries with non-standard event handler APIs. The change specifically addresses scenarios where React components (like echarts-for-react) expect event handlers to be passed as a dictionary object rather than individual props.

The new documentation section "Emulating Event Handler Behavior Outside a Component" provides a practical example showing how to override the create() classmethod in a custom component wrapper. The example demonstrates transforming an on_events prop containing a dictionary of event handlers into proper EventChain instances using rx.EventChain.create(). This approach allows developers to maintain Reflex's event handling paradigm while accommodating third-party React libraries that don't follow standard event handler prop conventions.

The addition integrates well with the existing wrapping documentation by extending the event handling coverage from simple cases (individual event handler props) to more complex integration scenarios. The documentation includes both JavaScript and Python code examples, maintaining consistency with the existing documentation style and providing clear, actionable guidance for developers working with challenging React library integrations.

Confidence score: 4/5

• This PR is safe to merge with minimal risk as it only adds documentation without changing any code functionality
• Score reflects clear, well-structured documentation that addresses a legitimate use case with practical examples
• No files require special attention as this is purely additive documentation

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