Add workflow to periodically check for dependency updates

[hvisser]

This adds a workflow to run ./gradlew versionCatalogUpdate and, if the catalog is updated, create a PR with the diffs. The workflow is scheduled to run once a week, and can be triggered manually too.

The heavy lifting is in the peter-evans/create-pull-request action that will manage creating and updating the PR when changes are detected. Because during the build gradlew is also changed, that change is reverted before creating the PR.

The PR does not give a comprehensive description of the changed dependencies, it merely produces a new branch and a diff. The created branch can be used to verify the dependency updates or do adjustments before merging, mainly serving as a reminder that updates are available.

The initial run will update the formatting of the catalog so that will be a bit noisy :)

[rock3r]

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