Update R chapter

[PabRod]

Changes in this PR

The R language kept evolving since we wrote this. It needs some updates

Checklist

SIGNIFICANT changes / additions, e.g. new chapters

• I checked whether the contribution fits in The Turing Way before considering contributing to this Guide.
• I discussed my contribution in an issue and took into account feedback.

ALL contributions

• I previewed my changes locally using e.g. python3 -m http.server 4000 and confirmed they work correctly.
• I checked for broken links, e.g. using the link checker GitHub Action workflow, or locally by using docker run --init -it -v `pwd`:/docs lycheeverse/lychee /docs --config=docs/lychee.toml, at least for the files I changed.
• My name was added to the CITATION.cff file.

[maltelueken]

Perhaps, we should also mention R Shiny?

[PabRod]

The broken links check throws 14 errors, but none of them in the file I edited.

[PabRod]

Ready to review and merge!

[maltelueken]

I made a correction about the pipe operators (my bad, |> was introduced in R 4.1) and added a link to Rcpp for perfomant R code.

Otherwise, the PR looks really great. With the correction, it can be merged.

[c-martinez]

I've suggested a couple of minor things to consider changing, but otherwise its looking great!

[bouweandela]

The R chapter as it currently is contains a lot of what Wikipedia would call "original research". It would be nice to replace this by a short introduction and references to established community standards.

[PabRod]

Dear @egpbos. @maltelueken and I consider this ready to be merged!

[egpbos]

Awesome effort here, thanks all!