title: how to remove header from all screens in react native (stackNavigator)
body: <p>I can not remove the header from all screens, I tried this setting below, but still the headers are not removed. Is it if I'm putting the navigationOptions settings incorrectly?</p>
  
  <pre><code>import React, {Component} from 'react';
  import {createAppContainer} from 'react-navigation';
  import {createStackNavigator} from 'react-navigation-stack';
  
  import Home from './telas/Home'
  import Login from './telas/Login'
  import Cadastro from './telas/Cadastro'
  
  
  const stackNavigator = createStackNavigator({
    Home:{
      screen:Home,
    },
    Login:{
      screen:Login
    },
    Cadastro:{
      screen:Cadastro
    },
  },
  {
    navigationOptions:{
      header:null
    }
  })
  
  const AppContainer = createAppContainer(stackNavigator);
  
  export default AppContainer;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/wkdJq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wkdJq.png" alt="enter image description here"></a></p>