.: Adding listing of implementations

* runc
* runv - https://groups.google.com/a/opencontainers.org/d/msg/dev/Tjq5QJ_eez0/LMt3dgReDQAJ
* ocp-testing - https://groups.google.com/a/opencontainers.org/d/msg/dev/_XUjuKzL84g/i2n5s0iUBgAJ

Signed-off-by: Vincent Batts <vbatts@redhat.com>

README.md

@@ -8,6 +8,7 @@ Table of Contents
 - [Container Configuration](config.md)
   - [Linux Specific Configuration](config-linux.md)
 - [Runtime and Lifecycle](runtime.md)
+- [Implementations](implementations.md)
 
 ## Use Cases
 

implementations.md

@@ -0,0 +1,16 @@
+# Implementations
+
+The following sections link to associated projects, some of which are maintained by the OCI and some of which are maintained by external organizations.
+If you know of any associated projects that are not listed here, please file a pull request adding a link to that project.
+
+## Runtime (Container)
+
+* [opencontainers/runc](https://github.com/opencontainers/runc) - Reference implementation of OCI runtime
+
+## Runtime (Virtual Machine)
+
+* [hyperhq/runv](https://github.com/hyperhq/runv) - Hypervisor-based runtime for OCI
+
+## Testing
+
+* [huawei-openlab/oct](https://github.com/huawei-openlab/oct) - Open Container Testing framework for OCI configuration and runtime