Fix linting and typo

packages/stack/example/src/HeaderBackgrounds.js

@@ -1,4 +1,4 @@
-import React, { Component } from 'react';
+import React } from 'react';
 import { StyleSheet, View, Text } from 'react-native';
 import { createStackNavigator } from 'react-navigation-stack';
 
@@ -71,7 +71,7 @@ function createHeaderBackgroundExample(options = {}) {
         },
       },
       News: {
-        screen: ({ navigation }) => (
+        screen: () => (
           <View style={styles.container}>
             <Text style={styles.tips} onPress={() => {}}>
               News Screen

packages/stack/example/src/HeaderPreset.js

@@ -1,5 +1,5 @@
 import * as React from 'react';
-import { Button, ScrollView, StatusBar } from 'react-native';
+import { Button, StatusBar } from 'react-native';
 import { SafeAreaView } from '@react-navigation/native';
 import { createStackNavigator } from 'react-navigation-stack';
 

packages/stack/example/src/StackWithDrawer.js

@@ -41,7 +41,7 @@ const Drawer = createDrawerNavigator(
   },
   {
     contentComponent: props => <Menu {...props} />,
-    navigationOptions: { title: 'Example' }
+    navigationOptions: { title: 'Example' },
   }
 );