title: Add HTML to popover title in ngx-bootstrap
body: <p>I'm trying to add a line break to a popover title in <code>ngx-bootstrap</code>.</p>
  
  <p>Is that possible? </p>
  
  <p>The line break tag below comes out as text, and for some reason <code>ng-template</code> seems to be within the popover body (not clear how to add title).</p>
  
  <pre><code>&lt;ng-template #popTemplate&gt;Just another: {{content}}&lt;/ng-template&gt;
  &lt;button type="button" class="btn btn-warning"
          [popover]="popTemplate" popoverTitle="Template ref &lt;BR&gt; content inside"&gt;
    TemplateRef binding
  &lt;/button&gt;
  </code></pre>
  
  <p><a href="https://stackblitz.com/edit/angular-ohncpd" rel="nofollow noreferrer">https://stackblitz.com/edit/angular-ohncpd</a></p>