use flake instead of shell

.envrc

@@ -1 +1 @@
-use nix
+use flake

flake.nix

@@ -21,8 +21,14 @@
         inherit nixpkgs system;
       };
 
-      devShell.${system} = import ./shell.nix {
+      devShells.${system} =
+        let
           pkgs = import nixpkgs { inherit system; };
+        in
+        {
+          default = pkgs.mkShell {
+            packages = with pkgs; [ git-crypt stylua ];
+          };
         };
     };
 }

shell.nix

@@ -1,8 +0,0 @@
-{ pkgs ? import <nixpkgs> { } }:
-
-pkgs.mkShell {
-  nativeBuildInputs = with pkgs; [
-    stylua
-    git-crypt
-  ];
-}