Add gauss-jordan_solution

For this issue, most of the work is done(check gauss_solution.m). With Gauss method you only reduce the elements down the main diagonal, while with Gauss-Jordan method you also reduce the elements up the main diagonal. The code for reducing the elements down the main diagonal is already written in gauss_solution.m

**You should add:**

- Code for reducing the elements up the main diagonal

- Change the code for finding the Solution Vector
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Other things to have in mind:
- we only find solution for linearly independent matrixes.
- add descriptive comments throughout the code.