title: Display Panel on button click
body: <p>I have created two panels. I want panel2 to be displayed below Panel1 on click of a button. What kind of listeners do i need to add in the button to make this happen? The example code is as follows</p>
  
  <pre><code>var panel1 = Ext.create('Ext.form. Panel', {
  
      layout: {
          type: 'vbox',
          align: 'stretch'
      },
      items: [{
          html: 'hello'
      },
      {
          xtype: 'button',
          text: 'click me'
      }]
  });
  
  var panel2 = Ext.create('Ext.form. Panel', {
  
      layout: {
          type: 'vbox',
          align: 'stretch'
      },
      items: [{
          html: 'world'}]
  });
  </code></pre>
  
  <p>here i want the html 'world' to be displayed after the button click. is there a way to do it?</p>