Create 12_PrintMatrix.cs

12. Write a program that reads from the console a positive integer number N (N < 20) and outputs a matrix like the following:
             N = 3
             1 2 3
             2 3 4
             3 4 5
              
             N = 4
             1 2 3 4
             2 3 4 5
             3 4 5 6
             4 5 6 7