Changes

Fix a bug when computing the Docker image version from which a container
has to be spawn to running the job making a build version of Silverpeas.

In the Silverpeas release pipeline, add a step of sending a reminder
email about tasks to do after just a release.

Improve the pipeline of publishing the community web site.

Improve the content of the email sent by the pipeline of preparing
the Docker image of Silverpeas for production.