message: Copied over system item typing and comments
diff: @@ -12,7 +12,13 @@ export function addNavigateHandlers(stateNavigator: StateNavigator | StateNaviga
  * Defines the Scene Props contract
  */
  export interface SceneProps {
  + /**
  + * The location of the scene in the stack
  + */
  crumb?: number;
  + /**
  + * Renders the scene for the State and data
  + */
  renderScene?: (state: State, data: any) => ReactNode;
  }
  @@ -35,8 +41,24 @@ export class RightBarIOS extends Component { }
  * Defines the Bar Button Props contract
  */
  export interface BarButtonIOSProps {
  + /**
  + * The button title
  + */
  title?: string;
  + /**
  + * The button image
  + */
  image?: ImageURISource;
  + /**
  + * The button system item
  + */
  + systemItem?: 'done' | 'cancel' | 'edit' | 'save' | 'add' | 'flexibleSpace'
  + | 'fixedSpace' | 'compose' | 'reply' | 'action' | 'organize'
  + | 'bookmarks' | 'search' | 'refresh' | 'stop' | 'camera'
  + | 'trash' | 'play' | 'pause' | 'rewind' | 'fastForward';
  + /**
  + * Handles button click events
  + */
  onPress?: () => void;
  }
  