Add subset problem in backtracking folder

[abhisek247767]

Problem statement:
Given an integer array nums of unique elements, return all possible subsets (the power set).The solution set must not contain duplicate subsets. Return the solution in any order.

Example 1:
Input: nums = [1,2,3]
Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]

[abhisek247767]

I am happy to contribute on that problem