Docker Ruby images used by Gitlab CI.

The following dependencies are being installed on all images:

• Node.js v22.12.0 (with npm)
• Google Chrome (latest stable)
• Chrome Webdriver (version 131.0.6778.85)

We currently have images for the following Rubies.

• latest Dockerfile
• 3.4 Dockerfile
• 3.3 Dockerfile
• 3.2 Dockerfile
• 3.1 Dockerfile
• 3.0 Dockerfile
• 2.7 Dockerfile

Dockerfiles are stored under folders for each version.

For updating the images, just open a pull request with the new Dockerfile version and, after accepted, Docker Hub will build automatically after a few minutes.

The images should setup an environment that is widely used, please don't install dependencies that are specific to a project. It's also good to have a pattern and all images support the same things, why a ruby version would use PhantomJS and the other doesn't?