fix(default): add overlay via nixos module system

For some reason, the overlays are discarded when the package set gets
re-evaluated.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

default.nix

@@ -25,6 +25,11 @@ let
 
   eval = evalModules {
     modules = [
+      {
+        nixpkgs.overlays = [
+          overlay
+        ];
+      }
       device.module
       liminix-config
     ];