1426. Any-Base Writer

A museum label printer can show numbers in any base from binary up to base 36, and the curators need a routine that prepares the text. Given the integer n and the base b, return the representation of n in base b as a string. Digits with values 0 to 9 are written as the characters 0-9 and values 10 to 35 as lowercase letters a-z. A negative n gets a single leading minus sign followed by the digits of its absolute value, there are no leading zeros, and zero is written as "0". Repeated division of the absolute value gives O(log n) time and O(log n) space for the answer.