input: Write a python function to count the number of words in an HTML document.
  assert count_words_in_html('<html><head><title>Test</title></head><body><p>Hello World!</p></body></html>') == 2
  assert count_words_in_html('<html><body><p>This is a test. This is only a test.</p></body></html>') == 8
  assert count_words_in_html('<html><head><title>Another Test</title></head><body><p>Testing, testing, 123.</p></body></html>') == 4
output: def count_words_in_html(html: str) -> int:
      from bs4 import BeautifulSoup
  
      soup = BeautifulSoup(html, 'html.parser')
      text = soup.get_text()
      words = text.split()
      
      return len(words)