message: docs: Add import line to router event example for clarification
  Without the `import {Event} from '@angular/router';`, the filter will
  not work because the type is understood as the native `Event`.
  Fixes
  PR Close
diff: @@ -27,12 +27,14 @@ export type NavigationTrigger = 'imperative'|'popstate'|'hashchange';
  * The following code shows how a class subscribes to router events.
  *
  * ```ts
  + * import {Event, RouterEvent, Router} from '@angular/router';
  + *
  * class MyService {
  - * constructor(public router: Router, logger: Logger) {
  + * constructor(public router: Router) {
  * router.events.pipe(
  * filter((e: Event): e is RouterEvent => e instanceof RouterEvent)
  * ).subscribe((e: RouterEvent) => {
  - * logger.log(e.id, e.url);
  + * // Do something
  * });
  * }
  * }
  