When a process inside the sxhkd scope is OOM killed, if the OOM policy
is set to `stop` then the sxhkd scope itself will exit, terminating
every process launched from the keyboard.
This is undesirable, set it to `continue` instead to keep other
processes running.
This option provides a more convenient way to overlay dummy packages.
It also adds a function `config.lib.test.mkStubPackage` that can,
e.g., be used for `package` options.
