Added jobs to create release notes

Description

This MR adds two jobs to be triggered upon creation of a (lightweight) tag:

• the first job creates the notes based on this mockup posted in the related issue.
• the second job creates the release with the notes prepared in preceding job.

Manual testing

This project was forked to https://gitlab.com/ebaque/cloud-deploy in order to test safely the creation of releases.

Here's the tested content in .gitlab-ci.yml: https://gitlab.com/ebaque/cloud-deploy/-/blob/release-with-image-digest/.gitlab-ci.yml

Creation of a lightweight tag:

Upon creation of this tag, the following pipeline triggered:

and this release was created:

Pulling the new docker image using using the digest is the same as pulling using latest:

Relates to gitlab#207379 (closed)