Support Gitlab Pipelines

[tillepille]

Describe Request:

I would love to use the validator in my GitLab pipelines.

At the moment I have to maintain my own image, maybe you could support this by adding a Docker build to the pipeline and provide it as an image in your existing Dockerhub org?

I would be happy to create a PR for a Dockerfile and the initial action but of course can't configure the credentials for the org.

Examples:

validate:
  stage: test
  image: roadiehq/backstage-entity-validator
  script:
  - validate-entity file1.yaml

Supporting Documentation Links:

• https://github.com/marketplace/actions/build-and-push-docker-images

[roadie-bot]

https://app.shortcut.com/larder/story/14590

[kissmikijr]

Hi! Thank you that would be awesome if you could contribute the Dockerfile and the action itself and we'll do the addition to publish it! Really appreciated!

[tillepille]

@kissmikijr I provided a PR as a proposal, happy to receive feedback on it!