Setup dependabot for Hugo

[roughike]

Right now, both Jekyll and Eleventy have dependabot configured so that they will get automatic update PRs whenever Jekyll/Eleventy has a newer version available. This is good because it ensures that these templates will continue working with the latest versions of Jekyll/Eleventy.

We need the same for Hugo, but at the moment, I'm not sure how it will work.

[remysheppard]

Perhaps hugo's modules feature?

[roughike]

How would that look like?

I had the idea of having a go.mod (or whatever is the Go equivalent for package.json) that has a dependency on Hugo and nothing else. The file would not be used for anything else than Dependabot yelling about new Hugo versions available.

I'm not too familiar with Go or Dependabot yet, but maybe there's an even better way to do it than that.