- build and test each platform separately on CI
- rework `Makefile` commands
- renew Docker tags description in README
Additionally:
- show output of failed tests
- ensure Docker images are not pulled in tests
- remove usage of deprecated `::set-output` GitHub Actions feature
- omit publishing and releasing Docker images in forks
- verify Git tag to match Makefile before releasing
- auto-cancel concurrent CI pipelines for the same Git ref