message: fix(alert): dismissibleChange emits boolean values
  `dismissibleChange` is used with `.subscribe((dismissible: boolean) => { ... })` but declared as `EventEmitter<string>`
diff: @@ -34,7 +34,7 @@ export class AlertComponent implements OnInit {
  public isClosed: boolean = false;
  public classes: string = '';
  - public dismissibleChange: EventEmitter<string> = new EventEmitter();
  + public dismissibleChange: EventEmitter<boolean> = new EventEmitter<boolean>();
  public constructor(_config: AlertConfig) {
  Object.assign(this, _config);
  