feat(xonsh): set up ssh-agent

flake.nix

@@ -100,6 +100,18 @@
           };
         };
         devShells.default = config.pre-commit.devShell;
+        devShells.haskell = pkgs.mkShell {
+          name = "haskell";
+          packages = builtins.attrValues {
+            inherit (pkgs) ghc;
+            inherit
+              (pkgs.haskellPackages)
+              cabal-install
+              haskell-language-server
+              ormolu
+              ;
+          };
+        };
         formatter = pkgs.alejandra;
       };
     };