Add nix files

* Build file
* Docker file

build.nix

@@ -0,0 +1,10 @@
+{ pkgs ? import <nixpkgs> {} }:
+let
+  rustPlatform = pkgs.rustPlatform;
+in
+  rustPlatform.buildRustPackage {
+    pname = "shifty-service";
+    version = "0.1";
+    src = ./.;
+    cargoHash = "sha256-bgtX30TGRlBjCZ8qbqNgovsZrZqJ9kEGlv/qv6T5uZA=";
+  }

docker.nix

@@ -0,0 +1,15 @@
+{ pkgs ? import <nixpkgs> {} }:
+let
+  shiftyService = import ./build.nix { inherit pkgs; };
+in pkgs.dockerTools.buildImage {
+  name = "shifty-backend";
+  tag = "0.1";
+
+  copyToRoot = pkgs.buildEnv {
+    name = "terminal-tools";
+    paths = [ pkgs.bash pkgs.coreutils pkgs.nix ];
+  };
+  config = {
+    Cmd = [ "${shiftyService}/bin/app" ];
+  };
+}