input: Write a python function to search for a substring within a list of strings.
  assert search_for_substring(["apple", "banana", "cherry"], "ban") == True
  assert search_for_substring(["apple", "banana", "cherry"], "berry") == False
  assert search_for_substring(["dog", "cat", "mouse"], "cat") == True
output: def search_for_substring(strings, substring):
      for s in strings:
          if substring in s:
              return True
      return False