Create a function that takes two dates and returns the number of days between the first and second date.
Examples
getDays(
new Date("June 14, 2019"),
new Date("June 20, 2019")
) ➞ 6
getDays(
new Date("December 29, 2018"),
new Date("January 1, 2019")
) ➞ 3
// Dates may not all be in the same month/year.
getDays(
new Date("July 20, 2019"),
new Date("July 30, 2019")
) ➞ 10