Update implementations, with PR feedback

Signed-off-by: Steve Lasker <stevenlasker@hotmail.com>

Author: SteveLasker

implementors.md

@@ -1,10 +1,12 @@
 # OCI Artifacts Implementations
 
-Projects or companies currently supporting OCI Artifacts
-
-* [Azure Container Registry](https://aka.ms/acr/artifacts)
-* [docker/distribution](https://github.com/docker/distribution/) - the reference implementation of the [OCI Distribution Spec][distribution-spec]
+Registries currently supporting OCI Artifacts
 
+- [Amazon Container Registry](https://aws.amazon.com/blogs/containers/oci-artifact-support-in-amazon-ecr/)
+- [Azure Container Registry](https://aka.ms/acr/artifacts)
+- [CNCF Distribution](https://github.com/distribution/distribution/) 
+- [Project Harbor](https://goharbor.io/blog/harbor-2.0/)
+- [Quay.io](https://www.openshift.com/blog/quay-oci-artifact-support-for-helm-charts)
 _(to add your project, please open a [pull-request](https://github.com/opencontainers/artifacts/pulls))_
 
 [distribution-spec]: https://github.com/opencontainers/distribution-spec/