[Suggestion] Use RenovateBot (or Scala Steward) for dependency upgrades

[gaeljw]

I've noticed #26 in which updating dependencies was done manually.

I would suggest setting up RenovateBot GitHub App (or optionally a scheduled GH Action) or Scala-Steward to get automated PRs for new dependencies.

I've got a slight preference for RenovateBot because it can also handle many other things that Scala Steward cannot but Scala Steward can be more useful for the "niche Scala stuff" like auto-reformatting when scalafmt is upgraded or better handling cross Scala versions declaration.

Merging can still be manual but at least we have a clear view of dependencies possible upgrades.