title: How to add a margin or padding to a Snackbar?
body: <p>I have been working on the Snackbar and achieved in my project successfully. However, there is this little thing which I want to add to Snackbar and that is the <code>margins</code>. I have seen in this link : <a href="https://material.io/design/components/snackbars.html#anatomy" rel="noreferrer">Snackbars - Material Design</a></p>
  <p>I really want my Snackbar to come like this :</p>
  <p><a href="https://i.stack.imgur.com/5gePc.png" rel="noreferrer"><img src="https://i.stack.imgur.com/5gePc.png" alt="Target Picture" /></a></p>
  <p>What I'm getting is this now :</p>
  <p><a href="https://i.stack.imgur.com/3F7DZ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/3F7DZ.png" alt="Resultant Picture" /></a></p>
  <p>My code is :</p>
  <pre><code>final snackBar = SnackBar(
      content: Text(&quot;Feild(s) are empty!&quot;),
      duration: new Duration(seconds: 1),
      backgroundColor: Theme.of(context).primaryColor,
    );
    Scaffold.of(context).showSnackBar(snackBar);
  }
  </code></pre>