feat(nix): Add basic Nix environment setup

.envrc

@@ -0,0 +1 @@
+use nix

default.nix

@@ -0,0 +1,11 @@
+{ pkgs ? (import <nixpkgs> { 
+    config.allowUnfree = true;
+}),
+}:
+pkgs.mkShell {
+  pure = true;
+  packages = with pkgs; [
+    # Choose the build tools that you need
+    act
+  ];
+}