Create ReactClassBuilder

[shogowada]

Many developers are more comfortable writing functions than classes. Create ReactClassBuilder that lets you create ReactClass purely by composing functions.

Draft (incomplete and highly likely to change, but just to demonstrate the idea):

case class ReactClassContext[WrappedProps, State](
  native: js.Dynamic,
  props: Props[WrappedProps],
  state: State
) {
  def setState(state: State): Unit = // ...
}

val reactClass: ReactClass =
    ReactClassBuilder[Props, State]()
        .shouldComponentUpdate((context: ReactClassContext[WrappedProps, State], nextContext: ReactClassContext[WrappedProps, State]) => Boolean)
        .render((context: ReactClassContext[WrappedProps, State]) => ReactElement)
        .build