title: Handling multitouch in flutter
body: <p>In <strong><em>flutter</em></strong>, there is a standard <strong><em>GestureDetector</em></strong> that allows to interprets  the commands <strong><em>"touch down"</em></strong>, <strong><em>"touch move"</em></strong> and <strong><em>"touch up"</em></strong> by means of the corresponding handlers:</p>
  
  <ul>
  <li>onPanStart: _handlePanStart,</li>
  <li>onPanUpdate: _handlePanUpdate,</li>
  <li>onPanEnd: _handlePanEnd,</li>
  </ul>
  
  <p>However, we are talking about processing a single touch, but what if I want to handle several parallel touches and movements? I.e. really use multitouch? Is there any kind of built-in control in flutter (maybe multitouch gesture detector, I don't known) that allows to get a vector or a list of events of clicks, movements, ups with ids of touches and their current coordinates? </p>