Added Counting Sort algorithm in C++

[dishantvyas15]

Description

Adding a code implementing the counting sort algorithm in C++. Reference: Fixes: #522

Type of change

• [x] New feature (non-breaking change which adds functionality)

Checklist:

• [x] I have read the contribution guidelines before making this PR.
• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented in my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation (Language folder or any other readme instructed to)
• [x] My changes generates no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works

[dishantvyas15]

@kaustubhgupta I've made the necessary changes. Review requested.

[dishantvyas15]

@kaustubhgupta Thank you for consideration..!

[kaustubhgupta]

@dishantvyas15 You're welcome. I am glad to share this that you are the 100th contributor to this repository! Congrats and all the best for future endeavors!

[dishantvyas15]

Wow, that's great 🥳🥳 @kaustubhgupta Good luck to you as well, for future triumphs!