Add more labels to Lagoon images

[tobybellwood]

This PR adds a fuller suite of docker labels to the Lagoon Images

e.g.

org.opencontainers.image.authors="The Lagoon Authors"
org.opencontainers.image.source="https://github.com/uselagoon/lagoon-images/blob/main/images/varnish/7.Dockerfile"
org.opencontainers.image.url="https://github.com/uselagoon/lagoon-images"
org.opencontainers.image.version="${LAGOON_VERSION}"
org.opencontainers.image.description="Varnish 7 image optimised for running in Lagoon in production and locally"
org.opencontainers.image.title="uselagoon/varnish-7"
org.opencontainers.image.base.name="docker.io/varnish:7-alpine"