title: In CKEditor, how can I add a "text" label to a button?
body: <pre><code>editor.ui.addButton( 'ImageUpload',{
                  label: 'Upload Image',
                  command: 'popup_image_uploader',
                  icon: this.path + 'images/icon.png'
              });
  </code></pre>
  
  <p>That's my current code right now. When you load the page, you only see the icon.</p>
  
  <p>But if you go to the demo <a href="http://ckeditor.com/demo">here</a>, you'll see that "Source" is a text.  I want to add the word "Upload Image" next to the icon.</p>