Revert "Remove package in flake.nix as we don't provide any"

This reverts commit 4d83e7e3af.

flake.nix

@@ -1,8 +1,30 @@
 {
   description = "Poetry2nix flake";
 
-  outputs = { self }:
+  outputs = { self, nixpkgs }:
+    let
+      # TODO: There must be a better way to provide arch-agnostic flakes..
+      systems = [ "x86_64-linux" "i686-linux" "x86_64-darwin" "aarch64-linux" ];
+      forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
+      # Memoize nixpkgs for different platforms for efficiency.
+      nixpkgsFor = forAllSystems (
+        system:
+        import nixpkgs {
+          inherit system;
+          overlays = [ self.overlay ];
+        }
+      );
+    in
     {
+
       overlay = import ./overlay.nix;
+
+      # TODO: I feel like `packages` is the wrong place for the poetry2nix attr
+      packages = forAllSystems (
+        system: {
+          inherit (nixpkgsFor.${system}) poetry poetry2nix;
+        }
+      );
+
     };
 }