Updated README

Author: giohappy

README

@@ -12,3 +12,13 @@ It replaces the configurations defined in the following locations:
 
 The [configurations](https://github.com/GeoNode/geonode-project/tree/master/docker) in the GeoNode Project repository will by default inherit from these base images without further configurations. These configurations can be customized inside projects for any specific need.
 
+## Builds and publishing to Docker Hub
+
+Docker images are built:
+
+- when a new commit is done to the master branch. This triggers build and updated of the published genode/{image}:latest
+- when a new release is pusblished. Tagging follows the {image}_{tag}, and a new geonode/{image}:{tag} is published.
+
+Example:
+ - A new commit changes a file under the `docker/geoserver` folder -> `geonode/geoserver:latest` is built and published to Docker Hub
+ - A release is done with the tag `postgis_15.1` -> `geonode/postgis:15.1` is built and published to Docker Hub