import { cnpjValidator } from "@burand/angular";
 
@Component({
  ...
})
export class RegisterComponent implements OnInit {
  ngOnInit() {
    this.form = this.formBuilder.group({
      name: [null, Validators.required],
      document: [null, [Validators.required, cnpjValidator]],
      password: [null, Validators.required],
    });
  }
}