Missing {renv} files

[pbbgss]

Normally there would be a renv/activate.R file included with the repo to automatically set up the environment and install what is declared in the renv.lock file on cloning. I would also expect a renv/.gitignore and possibly a renv/settings.json depending on the version of {renv}.

[pbbgss]

Or possibly may need the set-up instructions expanding to cover the "do you want to initialise renv?" question when running renv::restore()

[chloepugh]

Thanks! As a quick fix I've edited the setup instructions in this PR