Introduces the production of docker containers as a CI step.
Currently only provides a rolling-release version that builds
on every push to main. Images are deployed to ghcr.io.
The PR includes two variations on building the images. We'll
likely only want to stick with one or the other.
Adds a Dockerfile under the docker to package the corso binary.
This currently requires the user to build the corso binary (for linux/amd64) in the build image
prior to building the docker image. Follow up PRs will introduce a Makefile.
Also moves the build image to the build folder and adds a couple of README.md files with
instructions.
Fixes#218
