Add missing comma in README snippet

Author: rolandorojas

README.md

@@ -146,7 +146,7 @@ export class HomePage {
  componentProps: {
  src: "./assets/img/demo.jpg"
  },
- cssClass: 'ion-img-viewer'
+ cssClass: 'ion-img-viewer',
  keyboardClose: true,
  showBackdrop: true
  });