gitlint action: published image needs the docker:// prefix #223

.github/actions/gitlint/action.yml sets image: "jorisroovers/gitlint:0.19.1" for a using: "docker" action. Without the docker:// prefix the runner reads the value as a path to a Dockerfile in the repository, so the action fails before gitlint runs.

No workflow in this repository calls the action today, so nothing fails yet. Repositories created from the template inherit it.

Fix: image: "docker://jorisroovers/gitlint:0.19.1", or remove the action if it is not meant to be used.

Found by the Copilot review of eclipse-score/contributor_training#2, which carries the file unchanged.