input: Write a python function to sort a list of strings alphabetically, ignoring case.
  assert sort_strings_alphabetically(["Banana", "apple", "Cherry"]) == ["apple", "Banana", "Cherry"]
  assert sort_strings_alphabetically(["dog", "cat", "Bird", "elephant"]) == ["Bird", "cat", "dog", "elephant"]
  assert sort_strings_alphabetically(["zebra", "Monkey", "Alligator"]) == ["Alligator", "Monkey", "zebra"]
output: def sort_strings_alphabetically(strings):
      return sorted(strings, key=lambda s: s.lower())