Auto merge if pipeline succeeds

First of all, great project! I came across this project via your small advertisement in https://github.com/dependabot/dependabot-script/issues/452 😄. Used your helm chart to install dependabot and it all runs smooth and a lot faster than this dependabot-script project.

Now the reason for this new issue/ suggestion. Gitlab has the ability to auto merge MR's when the pipeline succeeds. The dependabot script also has support for this feature. It would be great if your dependabot-for-gitlab supports this feature as well.