message: docs: fix UniqueAlterEgoValidatorDirective
  * Use correct class name in providers
  * Update parameter & return signature for validate()
  PR Close
diff: @@ -16,7 +16,7 @@ import { Observable, of } from 'rxjs';
  providers: [
  {
  provide: NG_ASYNC_VALIDATORS,
  - useExisting: forwardRef(() => UniqueAlterEgoValidator),
  + useExisting: forwardRef(() => UniqueAlterEgoValidatorDirective),
  multi: true
  }
  ]
  @@ -26,9 +26,9 @@ export class UniqueAlterEgoValidatorDirective implements AsyncValidator {
  constructor(private heroesService: HeroesService) {}
  validate(
  - ctrl: AbstractControl
  - ): Promise<ValidationErrors | null> | Observable<ValidationErrors | null> {
  - return this.heroesService.isAlterEgoTaken(ctrl.value).pipe(
  + control: AbstractControl
  + ): Observable<ValidationErrors | null> {
  + return this.heroesService.isAlterEgoTaken(control.value).pipe(
  map(isTaken => (isTaken ? { uniqueAlterEgo: true } : null)),
  catchError(() => of(null))
  );
  