devShell with secrets management tools

.envrc

@@ -0,0 +1 @@
+use flake . --impure --allow-dirty --no-write-lock-file

flake.nix

@@ -175,7 +175,13 @@
         treefmtEval = treefmt-nix.lib.evalModule pkgs_unstable treefmtConf;
       in
       {
-        devShells.default = pkgs.mkShell { buildInputs = [ ]; };
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            sops
+            ssh-to-age
+            age
+          ];
+        };
         formatter = treefmtEval.config.build.wrapper;
         checks.formatting = treefmtEval.config.build.check self;
         # expose nixpkgs with overlay; TODO: figure out role of config