CI: Build Raspberry Pi images with GitHub Action (GitHub hosted runner)

- build the image under arm64 Docker Container, which runs on Fedora Vagrant VM and on GitHub hosted runner
- use cross-platform emulator collection on the Vagrant VM
- publish to S3 Bucket and put object tagging with aws CLI
- store images and logs as workflow Artifact (by default)
- put S3 Bucket download URLs to workflow's Summary
- send notification to Mattermost: AWS S3 links, Artifacts URLs

Fixes: #41

Author: yuravk