title: Angular 2 add multiple classes via [class.className] binding
body: <p>While adding a single class works great in this way - </p>
  
  <p><code>[class.loading-state]="loading"</code></p>
  
  <p>But how do I add multiple classes
  Ex if <code>loading</code> is <code>true</code> add class - <code>"loading-state" &amp; "my-class"</code> </p>
  
  <p>How do I get it done via the <code>[class] binding</code></p>