feat(flake): simplify flake template

flake.nix

@@ -1,7 +1,7 @@
 {
   description = "devshell";
 
-  outputs = { self }:
+  outputs = { self, nixpkgs }:
     let
       eachSystem = f:
         let
@@ -32,13 +32,20 @@
           legacyPackages = devshell;
           devShell = devshell.fromTOML ./devshell.toml;
         };
+      flakeTOML = inputs: path: eachSystem (system:
+        let pkgs = nixpkgs.legacyPackages.${system}.extend self.overlay;
+        in { 
+          devShell = pkgs.devshell.fromTOML path;
+        }
+      );
     in
     {
       defaultTemplate.path = ./template;
       defaultTemplate.description = "nix flake new 'github:numtide/devshell'";
       # Import this overlay into your instance of nixpkgs
       overlay = import ./overlay.nix;
       lib = {
+        inherit flakeTOML;
         importTOML = import ./nix/importTOML.nix;
       };
     }

template/flake.nix

@@ -2,19 +2,7 @@
   description = "virtual environments";
 
   inputs.devshell.url = "github:numtide/devshell";
-  inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  outputs = { self, flake-utils, devshell, nixpkgs }:
-    flake-utils.lib.eachDefaultSystem (system: {
-      devShell =
-        let pkgs = import nixpkgs {
-          inherit system;
-
-          overlays = [ devshell.overlay ];
-        };
-        in
-        pkgs.devshell.mkShell {
-          imports = [ (pkgs.devshell.importTOML ./devshell.toml) ];
-        };
-    });
+  outputs = { devshell, nixpkgs, ... }@inputs: 
+    devshell.lib.flakeTOML inputs ./devshell.toml;
 }