Add dependabot to fetch all latest dependencies

[whiskeyo]

Dependabot is a tool for fetching latest updates of packages that are used as dependencies for given project, and when there is some new version detected, it automatically creates the PR with updated version. Once the CI passes, the PR can be merged without worrying about breaking something.

It should probably be done after CI is added for every Wirego Remote, so there are tests that can verify changes.

To avoid having a spam of updates everyday, I'd suggest to set dependabot for every directory with:

schedule:
  interval: "weekly"