input: Write a python function to read a file and return the 10 most common words in it.
  assert most_common_words('text.txt')==['the', 'of', 'and', 'to', 'a', 'in', 'that', 'is', 'for', 'it']
  assert most_common_words('sample.txt')==['example', 'text', 'with', 'some', 'repeated', 'words', 'for', 'testing', 'this', 'function']
  assert most_common_words('empty.txt')==[]
output: def most_common_words(filename):
      from collections import Counter
      import re
  
      with open(filename, 'r') as file:
          text = file.read().lower()
          
      words = re.findall(r'\b\w+\b', text)
      word_counts = Counter(words)
      
      most_common = word_counts.most_common(10)
      return [word for word, count in most_common]