Taha Tesser c05a05e6fc Add ScrollNotificationObserver sample (#127023) ...

fixes https://github.com/flutter/flutter/issues/126702

### Preview

https://github.com/flutter/flutter/assets/48603081/4c529a0d-b8a5-4950-9095-429f1c5eccbb

2023-05-25 15:58:52 +00:00

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scroll_notification_observer.0_test.dart

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