Injectable bindings and bridge

[myers]

Hello! 您好

This builds on my work in https://github.com/alibaba/canvas-ui/pull/31, I suggest you will want to look at the last commit to understand this PR. When that other PR is merged I will update this PR and remove the draft designation.

This commit adds support for injecting custom event bindings into RenderCanvas and introduces BridgeEventBinding for programmatic event injection.

Changes:

• Add binding parameter to RenderCanvas constructor (defaults to DOMEventBinding)
• Add binding parameter to createElement factory function
• Implement BridgeEventBinding for programmatic event injection
• Add NativeEventBinding.el property for element binding
• Add comprehensive test suite for BridgeEventBinding (12 tests)

Benefits:

• Enables WebXR controller event injection
• Clean interface using property setter pattern