Run INN2 in an ISKME Docker container

[cclauss]

Related to:

• Run INN2 in a cclauss Docker container #24

Migrate https://github.com/cclauss/apt-get-inn2-docker --> https://github.com/ISKME/apt-get-inn2-docker

• Create a iskme/inn-docker GitHub repo and give me maintainer access. @aa-iskme
• Add repo Secrets (settings/secrets/actions) for DOCKER_USERNAME and DOCKER_PASSWORD. @aa-iskme
• Copy the contents of https://github.com/cclauss/apt-get-inn2-docker into that repo. @cclauss
• Generate a release to DockerHub similar to https://hub.docker.com/r/cclauss/inn/tags @cclauss
• Add iskme/inn-docker to our GitHub Actions and ensure the tests pass. @aa-iskme and @cclauss
• Remove cclauss/inn-docker from our testing. @cclauss