nix flake: add devShell

flake.nix

@@ -14,7 +14,6 @@
   };
 
   outputs = inputs @ {
-    self,
     nixpkgs,
     caps2esc,
     home-manager,
@@ -22,7 +21,9 @@
     peerix,
     sops-nix,
     ...
-  }: {
+  }: let
+    pkgs = nixpkgs.legacyPackages.x86_64-linux.pkgs;
+  in {
     nixosConfigurations = rec {
       nixy = nixpkgs.lib.nixosSystem {
         system = "x86_64-linux";
@@ -53,5 +54,13 @@
         ];
       };
     };
+
+    devShell.x86_64-linux = pkgs.mkShell {
+      buildInputs = with pkgs; [sops];
+      shellHook = ''
+        echo "Configuring NixOS!"
+      '';
+    };
+
   };
 }