Clarify working directory for lifecycle script execution

The documentation or the [initializeCommand](https://containers.dev/implementors/json_reference/#lifecycle-scripts) says:

> A command string or list of command arguments to run on the host machine before the container is created.

This is insufficient since it does not say anything about the working directory when the command is run.

This is a general problem with the reference documentation, every time something is run (on the host or in the container) the script writer needs to know the working directory.

PS. The same page uses "(list of) command arguments to run" but I cannot see that "command arguments" is defined anywhere, and it is not standard POSIX terminology. I find the term confusing since the immediate question then is "which command will get those 'command arguments' as its arguments?"