Create FibonacciChecker.js

Have the function FibonacciChecker(num) return the string yes if the number given is part of the Fibonacci sequence. This sequence is defined by: Fn = Fn-1 + Fn-2, which means to find Fn you add the previous two numbers up. The first two numbers are 0 and 1, then comes 1, 2, 3, 5 etc. If num is not in the Fibonacci sequence, return the string no.