Add a gitlab-ci file

The CI is configured to run the script tools/ci-job.sh on the memorekall-member image if and only if one of the following condition is true

• CI is triggered via web interface OR by a merge request
• The branch or commit contains the word `test
• The branch name is the default branc (main) or production

There is a script push_image_to_registry.sh which builds the image locally and push it to gitlab for CI.