refactor(flake-parts): initial flake-parts configuration

outputs/overlays/default.nix

@@ -0,0 +1,26 @@
+{ outputs, inputs, ... }:
+{
+  # For every flake input, aliases 'pkgs.inputs.${flake}' to
+  # 'inputs.${flake}.packages.${pkgs.system}' or
+  # 'inputs.${flake}.legacyPackages.${pkgs.system}'
+  flake-inputs = final: _: {
+    inputs = builtins.mapAttrs
+      (_: flake: let
+        legacyPackages = ((flake.legacyPackages or {}).${final.system} or {});
+        packages = ((flake.packages or {}).${final.system} or {});
+      in
+        if legacyPackages != {} then legacyPackages else packages
+      )
+      inputs;
+  };
+
+  zjstatus = final: prev: {
+    zjstatus = inputs.zjstatus.packages.${prev.system}.default;
+  };  
+
+  waybar = final: prev: {
+    waybar = inputs.nixpkgs-wayland.packages.${prev.system}.waybar;
+  };
+
+  additions = final: prev: import ../pkgs { pkgs = final; };
+}