[sarthakgupta1907-cell]

Describe your change:

Add implementation of the percentile algorithm in Maths/Percentile.js.

Calculates the nth percentile of an array using linear interpolation.

• Example: percentile([1, 2, 3, 4, 5], 50) => 3
• Example: percentile([1, 2, 3, 4, 5], 75) => 4

Checklist:

• I have read CONTRIBUTING. md.
• This pull request is all my own work—I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new JavaScript files are placed inside an existing directory.
• All filenames are in the format MyAlgorithmName.js -- PascalCase.
• All new algorithms have a URL in their comments that points to Wikipedia or another similar explanation.
• All new algorithms have tests, and the tests pass.
• All code is formatted with npx standard --fix .