RewardedAd missing steps

[beersheba]

There are missing steps in Section 9 (Add a rewarded ad):

• _loadRewardedAd() method is not called, should be called at the bottom of initState()

• _rewardedAd should be nullable

• _rewardedAd?.show requires to implement callback onUserEarnedReward: _rewardedAd?.show(onUserEarnedReward: (_, reward) {QuizManager.instance.useHint();},

[rickbsgu]

Thanks for this - I was really scratching my head.

Authors: How about fixing the tutorial??!!

[kunny]

Done updating the doc. Thanks for reporting!