Extra commands and directories to copy using `jk_cp` command.

`jk_cp` is a command provided by Jailkit package to copy files and directories into the chroot environment. The `jk_cp` command will also automatically handle and copy necessary library dependencies for binary files, ensuring that executables work correctly inside the chroot.

Instead of manually copying extra commands and all dependencies in the domain chroot directory, use this field to add extra commands (separated by space) to bring to into the chroot, ensuring that everything works as expected. For example to copy `rsync` and `zip` commands, put `rsync zip` in this field.