Watchtower: Auto container updates and notifications

[scottsweb]

Recieve a message when Watchtower has updated a container.

https://containrrr.github.io/watchtower/notifications/

[scottsweb]

Watchtower doesn't support Podman, so I need to investigate other methods of keeping containers up to date.

• compose-update script
• Automate Podman with Ansible
• Generating systemd unit files
• podman auto-update
• https://github.com/containers/podman-compose/issues/443

Related to #89