input: Write a function to find and sum all numbers in a string.
  assert find_numbers("15 apples, 4 bananas and 6 oranges")==25
  assert find_numbers("123 abc 456 def")==579
  assert find_numbers("no numbers here")==0
output: def find_numbers(s: str) -> int:
      import re
      numbers = re.findall(r'\d+', s)
      return sum(map(int, numbers))