Given a string indicating a range of letters, return a string which includes all the letters in that range, including the last letter. Note that if the range is given in capital letters, return the string in capitals also!
gimme_the_letters("a-z") ➞ "abcdefghijklmnopqrstuvwxyz"
gimme_the_letters("h-o") ➞ "hijklmno"
gimme_the_letters("Q-Z") ➞ "QRSTUVWXYZ"
gimme_the_letters("J-J") ➞ J"