How can I make my custom review stars display required in angular form

I have a form for adding reviews, and added a custom star rating component. The ‘rating’ form value is required, so it won’t let you submit without selecting a rating, but there is no feedback. So I would like it to highlight the review star section if it has no value on submit as if it were an angular form field.

<div class="stars-wrapper" title="Rating: {{ form.get('rating').value }} out of 5 stars">
  <div class="star-button-wrapper" *ngFor="let i of [1,2,3,4,5]">
    <button class="star-button" type="button" (click)="setRating(i)" attr.aria-label="Set Rating to {{i}} stars" >
       <mat-icon class="full-star" *ngIf="form.get('rating').value >= i">star</mat-icon>
       <mat-icon class="empty-star" *ngIf="form.get('rating').value < i">star_border</mat-icon>
    </button>
  </div>
</div>```