Add flake

flake.nix

@@ -0,0 +1,28 @@
+{
+  description = "Flake for exercism gleam track";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  };
+
+  outputs =
+    { nixpkgs, ... }:
+    let
+      systems = [ "x86_64-linux" ];
+    in
+    {
+      devShells = nixpkgs.lib.genAttrs systems (
+        system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+        in
+        {
+          default = pkgs.mkShell {
+            packages = [
+              pkgs.exercism
+            ];
+          };
+        }
+      );
+    };
+}