Add apkbuild-shellcheck?

atools is great and we began using apkbuild-lint outside of Alpine, in the pmaports repository of postmarketOS.

It would be great if we could also use apkbuild-shellcheck in the future, however the code for that is in the docker image "apkbuild-lint-tools" and not part of atools:

https://gitlab.alpinelinux.org/alpine/infra/docker/apkbuild-lint-tools/tree/master

@kdaudt, @Leo: are there plans to move apkbuild-shellcheck to atools, and/or would you accept patches to do this?