title: Two mat-slide-toggle with reactiveForms
body: <p>In reactive form I have two mat-slide-toggle (binded with one variable). But they don`t toggle together.
  Wenn I use [(ngModel)] everything is working. Unfortunately this solution does not suit me because mat-slide-toggle is a part of big form.</p>
  
  <p><a href="https://stackblitz.com/edit/angular-mvpfu5-xptpb7?file=app%2Fslide-toggle-overview-example.html" rel="nofollow noreferrer">https://stackblitz.com/edit/angular-mvpfu5-xptpb7?file=app%2Fslide-toggle-overview-example.html</a></p>