Added two icons to playground app

Removed stale code from ModalScreen as well.

playground/src/screens/ModalScreen.js

     };
   }
 
-  state = {
-    dimissCounter: 0,
-  }
-
-  componentDidMount() {
-    Navigation.events().bindComponent(this);
-  }
-
-  modalAttemptedToDismiss() {
-    return this.setState(state => ({ dimissCounter: state.dimissCounter + 1 }))
-  }
-
   render() {
     return (
       <Root componentId={this.props.componentId} footer={`Modal Stack Position: ${this.getModalPosition()}`}>