nix: set up build environment

[winny-]

No description provided.

[sector-f]

Idk anything about nix/nixos so I'm not in a position to tell you that this is wrong! 🥳

I would feel better if you could post some output showing this Works Right(tm) to this PR discussion, but it's not a big deal

[winny-]

this is how I use it:

winston@stargate ~/jh/jh_extract $ go build
go: command not found
winston@stargate ~/jh/jh_extract $ nix-shell

[nix-shell:~/jh/jh_extract]$ go build

[nix-shell:~/jh/jh_extract]$ go version
go version go1.18.2 linux/amd64