input: Write a function to crawl a given website and extract specific data, in this case, phone numbers. Return the extracted phone numbers or an empty list if none are found. 
  
  assert crawl_website_for_phone_numbers('www.example.com')==['123-456-7890']
  assert crawl_website_for_phone_numbers('www.anothersite.com')==[]
  assert crawl_website_for_phone_numbers('www.phones.com')==['555-555-5555', '123-456-7890']
output: import re
  import requests
  
  def crawl_website_for_phone_numbers(url):
      response = requests.get(f"http://{url}")
      if response.status_code != 200:
          return []
      phone_numbers = re.findall(r'\b\d{3}-\d{3}-\d{4}\b', response.text)
      return phone_numbers