title: Have multiple intervals in a staggered animation
body: <p>Hi I was wondering if it was possible to have a tween that can have multiple intervals in a staggered in serval e.g.</p>
  
  <blockquote>
    <p>opacity goes from 1.0 to 0.0 (% time: 0.45 to 0.5)</p>
  </blockquote>
  
  <p>then</p>
  
  <blockquote>
    <p>opacity goes from 0.0 to 1.0 (% time: 0.5 to 0.55)</p>
  </blockquote>
  
  <p>using a similar tween</p>
  
  <pre><code>opacity1 = Tween&lt;double&gt;(
        begin: 1.0,
        end: 0.0,
      ).animate(
        CurvedAnimation(
          parent: controller,
          curve: Interval(
            0.45, 0.5,
            curve: Curves.ease,
          ),
        ),
      ).NextTween&lt;double&gt;( ///Pseudo code
        begin: 0.0,
        end: 1.0,
      ).animate(
        CurvedAnimation(
          parent: controller,
          curve: Interval(
            0.5, 0.55,
            curve: Curves.ease,
          ),
        ),
      )
  </code></pre>