Adding SDK reference implementation to the runtimes set (#1132)

* Adding SDK reference implementation to the runtimes set

Signed-off-by: fjtirado <ftirados@redhat.com>

* Charles comments

Signed-off-by: fjtirado <ftirados@redhat.com>

---------

Signed-off-by: fjtirado <ftirados@redhat.com>
Co-authored-by: Charles d'Avernas <charles.davernas@neuroglia.io>

Author: fjtirado

README.md

@@ -90,6 +90,7 @@ No matter your preferred language, our SDKs provide the tools you need to levera
 | Name | About |
 | --- | --- |
 | [Apache KIE SonataFlow](https://sonataflow.org) | Apache KIE SonataFlow is a tool for building cloud-native workflow applications. You can use it to do the services and events orchestration and choreography. |
+| [Java SDK reference implementation](https://github.com/serverlessworkflow/sdk-java/tree/main/impl) | Full compliant Java implementation of the specification |
 | [Lemline](https://github.com/lemline/lemline) | Lemline is a highly scalable runtime running on top of your existing messaging infrastructure. |
 | [Synapse](https://github.com/serverlessworkflow/synapse) | Synapse is a scalable, cross-platform, fully customizable platform for managing and running Serverless Workflows. |