Write a function that splits a string into substrings of size n, adding a specified delimiter between each of the pieces.
splitAndDelimit("bellow", 2, '&') ➞ "be&ll&ow"
splitAndDelimit("magnify", 3, ':') ➞ "mag:nif:y"
splitAndDelimit("poisonous", 2, '~') ➞ "po~is~on~ou~s"N/A