Add module system basics & nix itself
diff --git a/modules/nix.nix b/modules/nix.nix
new file mode 100644
index 0000000..999068c
--- /dev/null
+++ b/modules/nix.nix
@@ -0,0 +1,20 @@
+{
+  pkgs,
+  registry,
+  ...
+}: {
+  config = {
+    nix = {
+      settings = {
+        experimental-features = ["nix-command" "flakes"];
+        auto-optimise-store = true;
+        keep-outputs = true;
+        flake-registry = "${registry}/flake-registry.json";
+      };
+      gc = {
+        automatic = true;
+        options = "--delete-older-than 7d";
+      };
+    };
+  };
+}
diff --git a/modules/secrets.nix b/modules/secrets.nix
index f891de7..cb55e20 100644
--- a/modules/secrets.nix
+++ b/modules/secrets.nix
@@ -1,8 +1,8 @@
-{ pkgs, ... }: {
-    config = {
-        environment.systemPackages = with pkgs; [
-            sops
-        ];
-        sops.defaultSopsFile = ../secrets/secrets.json;
-    };
+{pkgs, ...}: {
+  config = {
+    environment.systemPackages = with pkgs; [
+      sops
+    ];
+    sops.defaultSopsFile = ../secrets/secrets.json;
+  };
 }