Add graceful shutdown for Actions

[gbraad]

Observe from 'Hang around' step

until ! podman exec ... systemctl is-active --quiet countdown.timer
do
    sleep 5
done
# cleanup work ?
...
   podman exec ... echo -e "# Countdown timer reached.\n\nYou have 5 minutes remaining." > /tmp/countdown.md
   # trigger action inside the container?
   podman exec ... code /tmp/countdown.md
   sleep 300
...
echo "Finished by reaching countdown"

[gbraad]

https://github.com/gbraad-devenv/countdown-test
I am not convinced yet. This is more of a thing for use with a personal minecraft server; inform users of shutdown, and then copy world file as artifact.