How do I validate if the user has selected a `chip` in the `mat-chip-list` and also only when the user selects a `chip` form should become valid. Right now I have the `validators.required` set on the control, but it doesn't work.
This is what I have done so far:

---

HTML

```
<mat-chip-list formControlName="packageName">
   <mat-chip *ngFor="let pkg of packages" selected="true" style="background-color:#8d6e63">
        {{pkg.value}}
   </mat-chip>
</mat-chip-list>

```

---

TS

```
ngOnInit() {
  this.form = new FormGroup({
    'packageName': new FormControl('', Validators.required),
})

```