Implement a function that finds union of two sets. You can assume that the sets
are stored using arrays. So, if array1 = {1,2,3,4,5,6,3,2} and array2 is {1,3,5,7}, then
array3 should be {1,2,3,4,5,6,7}. Note array3 should not have any duplicate elements. You
have to:
think of all the functions that are required for this problem. Each function should perform
its dedicated task. So, plan them out before implementing them.
Main should only have a set of function calls.