Add Nix package and NixOS moodule

Add a Scribe Nix package and NixOS module to the flake that a user can
build and install.

Includes the following supporting changes:
- Adding a name and version to package.json to make Nix's mkYarnPackage
  happy
- Update laravel-mix to fix ERR_OSSL_EVP_UNSUPPORTED on newer nodejs
  versions

flake.nix

@@ -1,8 +1,21 @@
 {
-  inputs = { flake-utils.url = "github:numtide/flake-utils"; };
+  description = "Scribe";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
 
   outputs = { self, nixpkgs, flake-utils }:
-    flake-utils.lib.eachDefaultSystem (system:
-      let pkgs = nixpkgs.legacyPackages.${system};
-      in { devShell = import ./shell.nix { inherit pkgs; }; });
+    flake-utils.lib.eachDefaultSystem
+      (system:
+        let pkgs = nixpkgs.legacyPackages.${system};
+        in
+        {
+          devShell = import ./shell.nix { inherit pkgs; };
+          packages.default = pkgs.callPackage ./default.nix { };
+        })
+    // {
+      nixosModules.default = import ./module.nix self;
+    };
 }