input: Write a python function to find the starting index of a keyword in a given URL using regular expressions.
  assert find_keyword_starting_index("https://www.test.com/where-is-the-key", "key") == 29
  assert find_keyword_starting_index("https://www.example.com/no-key-here", "key") == 17
  assert find_keyword_starting_index("https://www.test.com/where-is-the-key", "notfound") == -1
output: import re
  
  def find_keyword_starting_index(url, keyword):
      match = re.search(keyword, url)
      if match:
          return match.start()
      return -1