The support for the base image alpine:3.12 will expire in 4 months (https://endoflife.date/alpine), so it would make sense to upgrade to the current version alpine:3.15.
I was able to create the acme.sh image with the new alpine:3.15 version without errors and also create and deploy a certificate, but further testing would be useful.
* `acme.sh`'s `ssh.sh` is probably one of the hooks that's most versatile
* By default, it's not installed on `alpine` docker images and therefore is lacking in the `acme.sh` docker image
* This change adds the `openssh` package and therefore the `ssh` and associated commands