add ionic fab in angualr code example

Example: ion-fab-button ionic angular

<ion-content>

  <!-- Fixed Floating Action Button that does not scroll with the content -->
  <ion-fab>
    <ion-fab-button>Button</ion-fab-button>
  </ion-fab>

  <!-- Default Floating Action Button that scrolls with the content.-->
  <ion-fab-button>Default</ion-fab-button>

  <!-- Mini -->
  <ion-fab-button size="small">Mini</ion-fab-button>

  <!-- Colors -->
  <ion-fab-button color="primary">Primary</ion-fab-button>
  <ion-fab-button color="secondary">Secondary</ion-fab-button>
  <ion-fab-button color="danger">Danger</ion-fab-button>
  <ion-fab-button color="light">Light</ion-fab-button>
  <ion-fab-button color="dark">Dark</ion-fab-button>

</ion-content>