title: Change value of radio button when input field changes
body: <p>I am having a radio button group with multiple values. One value is a custom value which needs to be set by an  field.</p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;mat-radio-group [(ngModel)]="timeout"&gt;
   &lt;mat-radio-button value="1"&gt;1 hour&lt;/mat-radio-button&gt;
   &lt;mat-radio-button value="6"&gt;6 hours&lt;/mat-radio-button&gt;
   &lt;mat-radio-button value="{{timer_cust}}"&gt;Custom&lt;/mat-radio-button&gt;
  &lt;/mat-radio-group&gt;
  
  &lt;mat-form-field&gt;
   &lt;input matInput type="number" placeholder="min" [(ngModel)]="timer_cust"&gt;
  &lt;/mat-form-field&gt;
  </code></pre>
  
  <p>When I check the radio "Custom", the correct value is reflected on "timeout" variable. But when I change the input value, "timer_cust" updates, but "timeout" sticks to the old value. How do I update "timeout" which is bound to the "mat-radio-group" as the input value changes?</p>