implemented quick sort algo using c#

[gabrielhs1357]

This PR implements the code for Quick Sort in C# referred in issue #40.

I have read the contributing guidelines in CONTRIBUTING.md and have ensured the following:

• [x] My code is placed in the required directory as outlined in CONTRIBUTING.md
• [x] My code file is named according to CONTRIBUTING.md
• [x] Variables, classes, functions etc. follow camel case as outlined in CONTRIBUTING.md
• [x] My code hasn't been implemented or claimed by someone else and I have checked the present issues and PRs for the same
• [x] My code is well commented
• [x] If my code is the first implementation of , I have added the link to this directory in README.md
• [x] I have not copied my code from anywhere

[codelixir]

Hey, @gabrielhs1357! according to this repo's CONTRIBUTING.md, you are supposed to comment on the corresponding issue (#40 in this case) before making a PR.

Merging this for now, but please keep this in mind in the future : )