Convert slice and splice challenge to lab and add to main repo

[jdwilkin4]

While campers have been doing better about understanding the concepts and problem solving with the new curriculum, they could still use extra practice with problem solving. So let's convert this slice and splice challenge from the legacy curriculum to a lab. Keep all users stories and problem description the same.

https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-algorithm-scripting/slice-and-splice

So this lab should go in the loops module, here

[ilenia-magoni]

are we sure we want to put this in the loops section? this can be solved without a loop pretty easily

we can put the condition that slice and splice and concat can't be used

[jdwilkin4]

slice and splice and concat can't be used

We shouldn't put conditions on these labs because we want campers to solve it however they like. That is what made those original challenges so good.
If we don't want to have it in the loops module, it can go in the JS fundamentals review module.

[ilenia-magoni]

review fundamentals sounds good 👍

[jdwilkin4]

It can go before the pyramid generator