title: How to align `TabBar` to the left with a custom starting position
body: <p>I'm currently working on a Flutter app in which I'd like to display the <code>TabBar</code> starting on the left. If an <code>AppBar</code> has a leading property I'd like to indent the starting position of the <code>TabBar</code> to match it. Then on the scroll, it would still pass through and not leave the white area.</p>
  <p>This is the code that I have that currently displays a <code>TabBar</code> in the middle of the <code>AppBar</code>:</p>
  <pre><code>AppBar(
    bottom: TabBar(
      isScrollable: true,
      tabs: state.sortedStreets.keys.map(
        (String key) =&gt; Tab(
          text: key.toUpperCase(),
        ),
      ).toList(),
    ),
  );
  </code></pre>