New member contribution for Nat.nthRoot

Stream: new members

[Francisco Unda]

I thought I would follow the contributing guide suggestion and post my first PR here to bring attention to it. I'm sure there are many things to improve it, so thanks to anyone taking a look, and let me know if this is not the right place to post this :) https://github.com/leanprover-community/mathlib4/pull/31492

[Snir Broshi]

Welcome! This channel is fine, a more specific one is #PR reviews if you want to bring attention to a PR, and in this specific case there's a thread about this issue where I think you should comment: #mathlib4 > Help wanted: proof in `Nat.nthRoot`