Added automatic nix store optimisation and garbage collection of versions older than 14 days

modules/configuration.nix

@@ -26,7 +26,15 @@
     }
   ];
   nix = {
-    settings.nix-path = config.nix.nixPath;
+    gc = {
+      automatic = true;
+      dates = "weekly";
+      options = "--delete-older-than 14d";
+    };
+    settings = {
+      auto-optimise-store = true;
+      nix-path = config.nix.nixPath;
+    };
     nixPath = ["nixpkgs=${inputs.nixpkgs}"];
   };