feat: Use r-lib/actions for reproducible environment

[mtwente]

Describe what feature you'd like. Pseudo-code, mockups, or screenshots of similar solutions are encouraged!

r-lib provides several Github Actions related to R projects/packages. I am going to look into whether it makes sense to use them for this project, e.g. for updating the renv lockfile and managing dependencies.

See https://github.com/r-lib/actions

What type of pull request would this be?

Enhancement

Any links to similar examples or other references we should review?

No response