Convert dev shell to flake

.envrc

@@ -0,0 +1,2 @@
+#shellcheck shell=bash
+use flake

flake.nix

@@ -0,0 +1,27 @@
+{
+  description = "GitHub Action that configures the Nix package manager to read from (and optionally write to) a remote cache.";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs";
+    flake-utils.url = "flake-utils";
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }@inputs:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in {
+        packages.nodejs = pkgs.nodejs-16_x;
+
+        devShells.default = pkgs.mkShell {
+          packages = [
+            self.packages.${system}.nodejs
+          ];
+        };
+      }
+    );
+}

shell.nix

@@ -14,10 +14,12 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-{ pkgs ? import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/0c408a087b4751c887e463e3848512c12017be25.tar.gz") {}
-}:
-
-with pkgs;
-mkShell {
-  packages = [ pkgs.nodejs-16_x ];
-}
+let
+  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  flakeCompatSource = fetchTarball {
+    url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+    sha256 = lock.nodes.flake-compat.locked.narHash;
+  };
+  flakeCompat = import flakeCompatSource { src = ./.; };
+in
+  flakeCompat.shellNix