R primer - current versions of key resources

There are updates to two of the suggested online books:
[R Programming for Data Science](https://bookdown.org/rdpeng/rprogdatascience/) by R.D. Peng was updated in 2022.
[R for Data Science](https://r4ds.hadley.nz/) has a 2nd edition, published in 2023, with an additional author.


