start handy on startup

modules/packages.nix

@@ -29,5 +29,17 @@
       jjui
       bat
     ];
+
+    systemd.user.services.handy = {
+      description = "Handy";
+      wantedBy = ["graphical-session.target"];
+      partOf = ["graphical-session.target"];
+      after = ["graphical-session.target"];
+      serviceConfig = {
+        ExecStart = "${self.packages.${pkgs.stdenv.hostPlatform.system}.handy}/bin/handy";
+        Restart = "on-failure";
+        RestartSec = 5;
+      };
+    };
   };
 }