onWin method
Records a win. Requests a review when the total is a multiple of
_reviewEveryNWins.
Implementation
Future<void> onWin() async {
final prefs = await ref.read(sharedPreferencesProvider.future);
final count = (state.value ?? 0) + 1;
await prefs.setInt(_key, count);
state = AsyncData(count);
if (count % _reviewEveryNWins == 0) {
await _maybeRequestReview();
}
}