Support component classes declared in JS

[greglittlefield-wf]

Not a clean diff: Depends on PRs #110 and #111

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Problem

#109 There wasn't a path to use React components declared in JS within react-dart.

Solution

• Add ReactJsComponentFactoryProxy to enable wrapping of JS components
• Add example of using JS components from within Dart
• Add index to example directory
• Add common factory proxy tests
• Deprecate jsify, add new jsifyAndAllowInterop
  • More closely matches jsify from package:js, and doesn't name-collide
• TODO:
  • tests around:
    • conditional event handler wrapping
    • wrapEventHandler
    • ReactJsComponentFactoryProxy construction

Testing

• Verify unit tests pass
• Verify example makes sense and works as expected

[jacehensley-wf]

Just for my own understanding, this is only necessary if you want a typed interface into your JS component correct? You could still call API methods on the component you just wouldn't get autocompletion or static analysis, right?

[greglittlefield-wf]

Good question; I'll clarify this in the comment.

For package:js, you actually have to declare the interop class to be able to call those methods on it. The typing, however, doesn't matter, so long as it is a @JS.

[greglittlefield-wf]

This will be added in some form as part of the upcoming react-dart 5.0.0 release