Add Deno to nix.

Chose to use nixos unstable otherwise version is lagging.

flake.lock

@@ -130,7 +130,8 @@
         "nixpkgs": [
           "cargo2nix",
           "nixpkgs"
-        ]
+        ],
+        "unstable": "unstable"
       }
     },
     "rust-overlay": {
@@ -157,6 +158,21 @@
         "repo": "rust-overlay",
         "type": "github"
       }
+    },
+    "unstable": {
+      "locked": {
+        "lastModified": 1678874551,
+        "narHash": "sha256-Gsq92n94Ikgmpxn7MsRhw+LXnQXo7KqgIG6tsLrpw3M=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "5979bc90e21e79c158fa9616bf405b829e0ab7b9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -10,6 +10,7 @@
     flake-utils.follows = "cargo2nix/flake-utils";
     nixpkgs.follows = "cargo2nix/nixpkgs";
     devshell.url = "github:numtide/devshell";
+    unstable.url = "github:nixos/nixpkgs";
   };
 
   outputs = {
@@ -18,6 +19,7 @@
     nixpkgs,
     flake-utils,
     devshell,
+    unstable,
   }:
     flake-utils.lib.eachDefaultSystem (
       system: let
@@ -26,6 +28,8 @@
           overlays = [cargo2nix.overlays.default devshell.overlays.default];
         };
 
+        deno = unstable.legacyPackages.${system}.deno;
+
         rustPkgs = pkgs.rustBuilder.makePackageSet {
           rustVersion = "1.64.0";
           packageFun = import ./Cargo.nix;
@@ -47,7 +51,9 @@
         ];
       in rec {
         inherit packages;
-        devShell = rustPkgs.workspaceShell {};
+        devShell = rustPkgs.workspaceShell {
+          packages = [deno];
+        };
         devShells = {
           aiken = pkgs.devshell.mkShell {
             name = "aiken";