Example configuration runners - gitlab

[JurrianFahner]

... Regarding your proposal about example GitLab projects, this sounds like a very good idea. What I would imagine (at least for now) is a community maintained project, that shows how the different executors have to be configured to work with Testcontainers. Ideally this would also help us in catching regressions with regards to GitLab CI.

Originally posted by @kiview in #4770 (review)

[JurrianFahner]

@kiview I've created an example with the default gitlab runner (docker in docker example): https://gitlab.com/testcontainers-examples/spring-boot-mongo-example

It would be nice to create also another runner configuration. But I need some small virtual machine to setup a gitlab-runner configuration. Are there facilities within the testcontainers project?