message: docs(hardware-back-button): IonRouterOutlet is an optional provider
diff: @@ -266,6 +266,7 @@ document.addEventListener('ionBackButton', (ev: BackButtonEvent) => {
  <TabItem value="angular">
  ```tsx
  +import { Optional } from '@angular/core';
  import { IonRouterOutlet, Platform } from '@ionic/angular';
  import { App } from '@capacitor/app';
  @@ -273,7 +274,7 @@ import { App } from '@capacitor/app';
  constructor(
  private platform: Platform,
  - private routerOutlet: IonRouterOutlet
  + @Optional() private routerOutlet?: IonRouterOutlet
  ) {
  this.platform.backButton.subscribeWithPriority(-1, () => {
  if (!this.routerOutlet.canGoBack()) {
  