Added flake.nix

flake.nix

@@ -0,0 +1,31 @@
+{
+  description = "Rust development environment";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-23.11";
+    nixpkgs-unstable.url = "nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs, nixpkgs-unstable }@inputs:
+  let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+      overlay-unstable = final: prev: {
+        unstable = nixpkgs-unstable.legacyPackages.${prev.system};
+      };
+    in {
+      devShells.x86_64-linux.default =
+        pkgs.mkShell {
+          nativeBuildInputs = with pkgs; [
+            fish
+            rustc
+            cargo
+          ];
+
+          shellHook = ''
+            echo "Running a nix development environment"
+            exec fish
+          '';
+        };
+  };
+}