title: How to add opacity transition for mapbox symbol layer
body: <p>I have a mapbox layer (created in studio) with different icons based on data conditions. Now I'm adding a toolbar to show and hide various icons based on the filter. This works great, but I want to adjust the transition to make it a bit smoother.</p>
  
  <p>I've read some posts about icon-opacity-transition, but it didn't work for me.</p>
  
  <pre><code>  map.setPaintProperty('layer-name', 'icon-opacity-transition', { "duration": 300 } );
  </code></pre>
  
  <p>results in  <strong>cannot read property 'value' of undefined</strong></p>
  
  <p>Is it possible to change the icon-opacity transition or is it at least possible to show and hide a layer with some custom transition values?</p>