Implement Quick Sort in C++ programming language

[neilchauhan2]

Implement Quick Sort in C++ programming language, with well explaining comments. Please make sure the code is easy to understand, since this repo is for beginners. Please create a separate file named, QuickSort.cpp.

[falafel72]

I'll work on this!

[Knee3]

I've created a PR(#31), please review the changes.