Create a function that returns a list of all the integers between two given numbers start and end.
range_of_num(2, 4) ➞ [3]
range_of_num(5, 9) ➞ [6, 7, 8]
range_of_num(2, 11) ➞ [3, 4, 5, 6, 7, 8, 9, 10]
start will always be <= end.start and end are NOT included in the final list.start == end, return an empty list.