title: Adding extra padding to TextSpan background in RichText widget
body: <p>I have a <code>RichText</code> with some <code>TextSpan</code>. I want one of the <code>TextSpan</code> widgets to have a background on it so I used <code>background: Paint()..color = Colors.redAccent</code> as its text style.</p>
  
  <p>Is there a way to add some extra red space/padding to the background.</p>
  
  <p>This is how it currently looks:</p>
  
  <p><a href="https://i.stack.imgur.com/H0qJ9.png" rel="noreferrer"><img src="https://i.stack.imgur.com/H0qJ9.png" alt="before padding on text"></a></p>
  
  <p>This is how I want it to look (notice the extra red on the top and bottom of the highlighted text):</p>
  
  <p><a href="https://i.stack.imgur.com/Ksnuu.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Ksnuu.png" alt="after padding on text (desired)"></a></p>
  
  <p>This is the code used:</p>
  
  <pre><code>Scaffold(
    appBar: new AppBar(),
    body: new RichText(
      text: new TextSpan(
        text: 'This is a one the lines in the span \n ',
        style: TextStyle(fontSize: 15.0, color: Colors.black),
        children: &lt;TextSpan&gt;[
          new TextSpan(
              text: 'This is the second line',
              style: new TextStyle(fontWeight: FontWeight.bold)),
          new TextSpan(
              text: ' background on me ',
              style: new TextStyle(
                fontWeight: FontWeight.bold,
                background: Paint()..color = Colors.redAccent,
              )),
          new TextSpan(text: ' This is another of the lines in the span!'),
        ],
      ),
    ), // This trailing comma makes auto-formatting nicer for build methods.
  )
  </code></pre>
  
  <p>I tried adding <code>height</code> to the text style, but it doesn't affect the height of the background.</p>