I currently have a bookdown project which relies on many R packages. I would like to keep a "snapshot" of this project so that in the future, I am able to run it using the same R package versions as before. Is there a straightforward way to specify exactly the R versions for each of the packages I use? For example, one of them is fdrtool which I'd like to force whatever future user to use at version 1.2.15. Thank you.