Added Stack iteration quick sort for visualization.

[thetornadotitan]

Hello Dan,

I have implemented a visualization for quick sort using the stack object to handle the recursive calls iteratively.

The main issue with trying to visualize quickdraw is that it uses recursion and you have to break that recursion into an iterative process so you can view each step in the iteration.

Using the Stack object allows this. You'll see in a comment in the code that this was not my design or finding but rather I found someone who cleverly broke the recursion and used that as a basis.

Originally I made the quicksort to be used in continuation of the pixel sorting video you did. However, I saw the visualisation video and decided to help there as well.

Hopefully, this is useful.

Thank for your time!

[thetornadotitan]

Forgive me if I have broken any formalities with git, this is my first commit to something that is not my own. :)