virtualbox: add friedrichaltheide to maintainers

pkgs/applications/virtualization/virtualbox/default.nix

···
     ];
     license = licenses.gpl2;
     homepage = "https://www.virtualbox.org/";
-    maintainers = with maintainers; [ sander ];
+    maintainers = with maintainers; [ sander friedrichaltheide ];
     platforms = [ "x86_64-linux" ];
     mainProgram = "VirtualBox";
   };