Fibonacci: Added iterative and recursive solution for fibonacci

[miladmikeal]

Description of new feature, or changes

This PR adds the solution for fibonacci, both iterative and recursive. It also adds tests.

Checklist

• [x] Your branch is up-to-date with the base branch
• [x] You've included at least one test if this is a new feature
• [x] All tests are passing

Related Issues and Discussions

https://github.com/manrajgrover/algorithms-js/issues/10