Summary:
`CheckBox` component was introduced in v0.49.0 and not implemented on iOS.
Users who are trying to use `CheckBox` on iOS will get a warning that
> Native component for "AndroidCheckBox" does not exist
We should declare in the document that this component is Android only and use `UnimplementedView` for iOS.
- Use `react-native init` new project
- Apply pull request changes
- Add `<Checkbox />` after welcome text in `App.js`
- Run the app in iOS simulator
Closes https://github.com/facebook/react-native/pull/16211
Differential Revision: D6005393
Pulled By: hramos
fbshipit-source-id: 1c9b68b5e1c933496c4d7c2f487f0500264b603a
Tim Wang