Add OCI standard annotation labels to every build

This provides every build with basic labels defined by the OCI standard for annotations[1]. This includes the project URL, the exact commit an image is built from, the build time and date as well as the project title and description.

1: https://github.com/opencontainers/image-spec/blob/79b036d80240ae530a8de15e1d21c7ab9292c693/annotations.md