Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.
Note: You must not use any built-in BigInteger library or convert the inputs to integer directly.
1 <= num1.length, num2.length <= 200num1 and num2 consist of digits onlynum1 and num2 do not contain any leading zero, except the number 0 itselfnum1 = "2", num2 = "3""6"num1 = "123", num2 = "456""56088"