feat(recursiveFibonacci): create exercise

[nik-rev]

Because

It was decided to add new recursion exercises

This PR

• Adds new exercise

Issue

Related to #27265

Additional Information

Pull Request Requirements

• [x] I have thoroughly read and understand The Odin Project Contributing Guide
• [x] The title of this PR follows the location of change: brief description of change format, e.g. 01_helloWorld: Update test cases
• [x] The Because section summarizes the reason for this PR
• [x] The This PR section has a bullet point list describing the changes in this PR
• [x] If this PR addresses an open issue, it is linked in the Issue section
• [x] If this PR includes any changes that affect the solution of an exercise, I've also updated the solution in the /solutions folder

[mao-sz]

@JoshDevHub How would you like fib/mergeSort to be handled?

[JoshDevHub]

I'm not 100% sure what to do about these yet, and it'll require a bit more discussion with the team I think. Like going ahead with this would probably mean dissolving the current recursion project and orphaning all existing submissions. Is that worth having a TDD experience? Maybe, maybe not.

In any case, I think this can be tackled independently from the other recursion exercises, which are more straightforward to add in.