chore: add n-th Fibonacci number lab

[Dario-DC]

Checklist:

• [x] I have read freeCodeCamp's contribution guidelines.
• [x] My pull request has a descriptive title (not a vague title like Update index.md)

Closes #474

[zairahira]

It seems like the code is following a recursive approach rather than a dynamic approach. The goal of this lab isn't recursion according to the issue description.

[Dario-DC]

I refactored the code to use a bottom-up approach. This should count as dynamic @zairahira

I'm asking to create an array in the global scope to store the computed sequence numbers because I thought it would be easier to test. I'm not sure, though.

[zairahira]

This version implements the dynamic approach and it's looking good 🎉

[Dario-DC]

Good catch, I didn't realized it @moT01

[moT01]

The prototype doesn't fulfill the user stories anymore. "You should define an empty array named sequence in the global scope." We should either adjust the user story, or write a different solution that starts with an empty array.

[Dario-DC]

The prototype doesn't fulfill the user stories anymore. "You should define an empty array named sequence in the global scope." We should either adjust the user story, or write a different solution that starts with an empty array.

My bad, I updated the name and forgot to fix the rest accordingly.