title: How to set fill color for selection in fabricjs?
body: <p>I'd like to select a bunch of objects on fabricjs(2.7.0) canvas and show selection as filled with low opacity.</p>
  
  <p><strong>Current</strong>:
  <a href="https://i.stack.imgur.com/mzf7B.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/mzf7B.png" alt="enter image description here"></a></p>
  
  <p><strong>Desired</strong>:
  <a href="https://i.stack.imgur.com/G4y9Z.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/G4y9Z.png" alt="enter image description here"></a></p>
  
  <p>I tried this:</p>
  
  <pre><code>fabric.Group.prototype.selectionBackgroundColor = '#2dcfab';
  fabric.Group.prototype.backgroundColor = '#2dcfab';
  </code></pre>
  
  <p>But no luck. here is the <a href="https://jsfiddle.net/mudin/Lj2eofk1/1/" rel="nofollow noreferrer">jsfiddle</a>. Any help would be appreciated!</p>