Archive project now that work is complete

Fixes #118.

Author: michaelb990

README.md

@@ -1,3 +1,6 @@
+## Project Status
+This project's work has been proposed to the [OCI Reference Types Working Group](https://github.com/opencontainers/wg-reference-types) and has now been archived.
+
 # ORAS Artifacts Specification
 
 [OCI Artifacts][oci-artifacts] generalized the ability to persist artifacts within an [OCI Distribution conformant][oci-conformance] registry enabling a wide range of *individual* artifacts.