input: Write a function to crawl a website and extract all phone numbers from its content. Ensure the phone numbers are in the format '###-###-####'. The function should return a list of all found phone numbers.
  assert crawl_website_for_phone_numbers('www.example.com')==['123-456-7890', '987-654-3210']
  assert crawl_website_for_phone_numbers('www.sample.com')==['555-555-5555']
  assert crawl_website_for_phone_numbers('www.test.com')==[]
output: import re
  import requests
  
  def crawl_website_for_phone_numbers(url):
      response = requests.get(url)
      content = response.text
      phone_numbers = re.findall(r'\b\d{3}-\d{3}-\d{4}\b', content)
      return phone_numbers