Given a current time in the string format HH:MM and a number of minutes, return the clock time given those minutes added to the base time. Assume you're working with a standard 12-hour clock and the output should match the input format HH:MM.
addMinutes('1:30', 30); // 2:00
addMinutes('12:30', 40); // 1:10
addMinutes('11:59', 1); // 12:00