Add OpenSearch Dev Services to 3.4.1 announcement

Author: gsmet

_posts/2023-09-29-quarkus-3-4-1-released.adoc renamed to _posts/2023-09-20-quarkus-3-4-1-released.adoc

@@ -53,6 +53,13 @@ It is now possible to entirely disable the automatic setup of the Flyway extensi
 
 You can also make Flyway inactive for a specific datasource by setting `quarkus.flyway.active=false` for the default datasource or `quarkus.flyway."datasource name".active=false` for a named datasource.
 
+=== OpenSearch Dev Services
+
+Dev Services can now start an OpenSearch container,
+either automatically when using Hibernate Search with OpenSearch or manually by setting the distribution with `quarkus.elasticsearch.devservices.distribution=opensearch`.
+
+More information in https://quarkus.io/guides/elasticsearch-dev-services#configuring-the-image[our documentation].
+
 == Full changelog
 
 You can get the full changelog of https://github.com/quarkusio/quarkus/releases/tag/3.4.0.CR1[3.4.0.CR1], https://github.com/quarkusio/quarkus/releases/tag/3.4.0[3.4.0], and https://github.com/quarkusio/quarkus/releases/tag/3.4.1[3.4.1] on GitHub.