Write a function that returns True if a year is a leap, otherwise return False.
A year is a "leap year" if it lasts 366 days, instead of 365 in a typical year. That extra day is added to the end of the shortest month, creating February 29.
A leap year occurs every four years, and will take place if the year is a multiple of four. The exception to this is a year at the beginning of a century (for example, 1900 or 2000), where the year must be divisible by 400 to be a leap year.
leap_year(1990) ➞ False
leap_year(1924) ➞ True
leap_year(2021) ➞ False