Merge branch 'issues/12'

* issues/12:
  pyproject.toml: Update project version to 0.2.0
  README: Extend with information on arch-release-sync
  example.toml: Add synchronization related documentation
  Add script entrypoint for arch-release-sync
  cli: Add entrypoint for arch-release-sync
  files: Add ProjectFiles class to handle synchronization
  gitlab: More explicit print when downloading build artifacts
  gitlab: Implement download of promotion artifact
  argparse: Add parser for arch-release-sync
  gitlab: Change signature of constructor
  gitlab: More generically retrieve types of releases
  config: Make PRIVATE_TOKEN optional
  config: Add integration to configure synchronization
4 jobs for 0.2.0 in 1 minute and 33 seconds (queued for 9 seconds)