add cosmic config

flake.nix

@@ -6,6 +6,8 @@
     disko.inputs.nixpkgs.follows = "nixpkgs";
     home-manager.url = "github:nix-community/home-manager/master";
     home-manager.inputs.nixpkgs.follows = "nixpkgs";
+    nixos-cosmic.url = "github:lilyinstarlight/nixos-cosmic";
+    nixos-cosmic.inputs.nixpkgs.follows = "nixpkgs";
     nixos-hardware.url = "github:NixOS/nixos-hardware/master";
     stylix.url = "github:danth/stylix";
     stylix.inputs.nixpkgs.follows = "nixpkgs";
@@ -15,6 +17,7 @@
     self,
     nixpkgs,
     nix,
+    nixos-cosmic,
     nixos-hardware,
     home-manager,
     stylix,
@@ -68,7 +71,16 @@
         };
       };
       loki = lib.nixosSystem {
-        modules = [./hosts/loki];
+        modules = [
+          {
+            nix.settings = {
+              substituters = ["https://cosmic.cachix.org/"];
+              trusted-public-keys = ["cosmic.cachix.org-1:Dya9IyXD4xdBehWjrkPv6rtxpmMdRel02smYzA85dPE="];
+            };
+          }
+          nixos-cosmic.nixosModules.default
+          ./hosts/loki
+        ];
         specialArgs = {
           inherit inputs outputs;
         };