input: Write a function to read in a tweet and remove all punctuation, special characters and stopwords. If the input tweet is empty, return an empty list.
  assert remove_unwanted_elements("I'm so excited to be going to the #MuseumTour! #BigDay #travel")==['excited', 'going', 'MuseumTour', 'BigDay', 'travel']
  assert remove_unwanted_elements("#1Fan")==['1Fan']
  assert remove_unwanted_elements("")==[]
output: def remove_unwanted_elements(tweet):
      import re
      from nltk.corpus import stopwords
      stop_words = set(stopwords.words('english'))
      words = re.findall(r'\b\w+\b', tweet)
      filtered_words = [word for word in words if word.lower() not in stop_words]
      return filtered_words