input: Write a function to count the frequency of words in a list.
  assert count_words(["Apple", "Banana", "Apple", "Mango", "Banana"]) == {"Apple": 2, "Banana": 2, "Mango": 1}
  assert count_words(["Hello", "World", "Hello", "AI"]) == {"Hello": 2, "World": 1, "AI": 1}
  assert count_words(["Cat", "Dog", "Cat", "Dog", "Mouse"]) == {"Cat": 2, "Dog": 2, "Mouse": 1}
output: def count_words(word_list):
      word_count = {}
      for word in word_list:
          if word in word_count:
              word_count[word] += 1
          else:
              word_count[word] = 1
      return word_count