Add a -1 that works similar to -0 but exits

[darkfeline]

This is a feature request to add a -1 option ("oneshot") that works like -0 but exits after the bootstrap instead of continuing to run.

The use case is that even though I start inputplug -0 in my .xinitrc, when everything settles there are some actions that haven't taken effect or have been overridden by some unknown async init step.

Is this a feature you would want to add? If so, would you add it or would you prefer a PR? I don't know Rust but the code looks straightforward enough that I could probably do it.