Consider adding Nix flakes to the templates

There was a guy at the workshop today and spent some time setting up a Nix flake so I was like "hmm maybe we can include that in the template", so that's why I wanted to bring this up for discussion.

Probably should've created a Discussion instead...

Ok, I understand why you're asking for this, but not what problem it would solve (why do we need this?) An issue is fine as we don't have a lot of discussions on this repo. If you see the guy again, can you link them to this issue and ask what benefits would be had by adding a nix flake to the templates?

Sure, I'll wait him to show up here

Nix Flakes allow for reproducible environment, declarative configuration, and builds, plus they work cross platform. Additionally, devShells + direnv allow for seamless development on a project with all the packages you need declared in a repo, so you don't need to have them installed system-wide.

I use NixOS as my daily driver so I'm used to setting up flakes for my projects but still, I think it may be a cool addition as a parameter or something.