refactor: pull bootstap into regular shell for ease of use

nixpkgs.nix

@@ -0,0 +1,9 @@
+# A nixpkgs instance that is grabbed from the pinned nixpkgs commit in the lock file
+# This is useful to avoid using channels when using legacy nix commands
+let
+  lock = (builtins.fromJSON (builtins.readFile ./flake.lock)).nodes.nixpkgs.locked;
+in
+  import (fetchTarball {
+    url = "https://github.com/nixos/nixpkgs/archive/${lock.rev}.tar.gz";
+    sha256 = lock.narHash;
+  })