title: Add an asterisk to a label if field is required
body: <p>I have a label that I want to add an asterisk to if field is required. I have tried applying <code>ng-class</code> like so</p>
  
  <pre><code>&lt;div class="col-xs-12 top5"  ng-if="(activity.itemType=='TEXTAREA')"&gt;
       &lt;label class="col-xs-3 control-label text-right" for="act4{{$index}}"
              ng-class="{'asterisk-if-mandatory': data[$index].mandatory}"&gt;{{activity.itemLabel}}&lt;/label&gt;
       &lt;div class="col-xs-9"&gt;
           &lt;textarea ng-model="activityItems[$index].value"
                     ng-required="data[$index].mandatory" cols="40" rows="6"
                     id="act4{{$index}}" name="txtComments" class="defaultTextareaInput"&gt;&lt;/textarea&gt;
       &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and then css</p>
  
  <pre><code>.asterisk-if-mandatory {
      content: " *"
  }
  </code></pre>
  
  <p>Any solutions?</p>