title: TextButton Full Width
body: <p>I am creating a gmail add-on using app script. According to design requirement I want to create a TextButton which is full width i.e. It covers the entire width of the add on.
  I am using TextButton class for this as below -</p>
  <pre><code>var textButton = CardService.newTextButton()
      .setText(btnName)
      .setOnClickAction(action)
      .setTextButtonStyle(CardService.TextButtonStyle.FILLED);
  </code></pre>
  <p>Can anyone please confirm how can I make this button full width?
  TIA.</p>