input: Write a python function to manage quiz scores, including adding scores and calculating the average.
  assert quiz.get_average() == 0
  quiz.add_score('Alice', 90)
  assert quiz.get_average() == 90
  quiz.add_score('Bob', 80)
  assert quiz.get_average() == 85
  quiz.add_score('Charlie', 70)
  assert quiz.get_average() == 80
output: class Quiz:
      def __init__(self):
          self.scores = []
  
      def add_score(self, name, score):
          self.scores.append(score)
  
      def get_average(self):
          if not self.scores:
              return 0
          return sum(self.scores) / len(self.scores)
  
  quiz = Quiz()