implementations: Link to mrunalp/ocitools

Mrunal mentioned this during today's meeting, and linking to it will
hopefully reduce the amount of duplicated effort in this area.

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

implementations.md

@@ -11,6 +11,10 @@ If you know of any associated projects that are not listed here, please file a p
 
 * [hyperhq/runv](https://github.com/hyperhq/runv) - Hypervisor-based runtime for OCI
 
+## Bundle authoring
+
+* [mrunalp/ocitools](https://github.com/mrunalp/ocitools) - A config generator.
+
 ## Testing
 
 * [huawei-openlab/oct](https://github.com/huawei-openlab/oct) - Open Container Testing framework for OCI configuration and runtime