baseos docker image build workflow

[glemieux]

### Tasks
- [x] Develop amd64 build version
- [x] Develop arm64 build version

[glemieux]

Testing the baseos image by trying to generate a known working upstream (e.g. elm-fates) image build process would require building the elm-fates using the main branch of the repository.

For a pull request, it might be useful to load the image to a local registry instead of pushing to the official dockerhub registry. See here: https://docs.docker.com/build/ci/github-actions/local-registry/. As such, the build would only be pushed if it passed tests and was merged to main. This means that any changes to main should really be merged into the pull request branch during testing, which would need to be automated.

[glemieux]

Using the official docker platform emulation via github works and doesn't seem to struggle with #12 currently. The build does take a long time, which is not unexpected given emulation + building multiple packages from source, so it would be good to figure out how to leverage existing build layers to reduce future update build times.

• [ ] Review if github build will pull from pre-existing image or if uploading artefact is necessary
• [ ] Review cache options

[glemieux]

Moving testing tasks to a new issue to be addressed via a different pull request: #19