input: Write a function to crawl a website for phone numbers and return a list of all phone numbers found. If no phone numbers are found, return an empty list.
  
  assert crawl_website_for_phone_numbers('www.example.com')==['123-456-7890', '987-654-3210']
  assert crawl_website_for_phone_numbers('www.anothersite.com')==['111-222-3333']
  assert crawl_website_for_phone_numbers('www.nosuchdata.com')==[]
  assert crawl_website_for_phone_numbers('www.example.com/anotherpage')==['555-555-5555']
  assert crawl_website_for_phone_numbers('www.invalidurl.com')==[]
output: def crawl_website_for_phone_numbers(url):
      import re
      import requests
      try:
          response = requests.get(f'http://{url}')
          response.raise_for_status()
          phone_numbers = re.findall(r'\b\d{3}-\d{3}-\d{4}\b', response.text)
          return phone_numbers
      except:
          return []