adding nqueens,quicksort,selctionsort

[VishalVR-21]

Description

I have added nqueens,quicksort and selection sort

Related Issue

This PR closes #

Motivation and Context

Screenshots (if any)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.

[github-actions[bot]]

Hey @VishalVR-21!, thank you for contributing to open source!🚀 Your pull request will be reviewed at the earliest.

[VishalVR-21]

Sir may i know why is my pull request not accepted