input: Write a python function to check if a keyword exists in the content of a given URL.
  assert check_if_keyword_exists("https://en.wikipedia.org/wiki/Python_(programming_language)", "python") == True
  assert check_if_keyword_exists("https://en.wikipedia.org/wiki/Python_(programming_language)", "java") == False
  assert check_if_keyword_exists("https://www.python.org", "programming") == True
output: import requests
  
  def check_if_keyword_exists(url, keyword):
      response = requests.get(url)
      content = response.text.lower()
      return keyword.lower() in content