Add pages for R4.0.5/ R4.1.0 docs

[lvanacken]

(created for @richierocks to close out an internal Ticket)

Currently, all pages are limited to what is used in R3.6.2, which is really out of date (from Dec 2019).

R4.0.5 is released in April 2021, and R 4.1.0 is due for May 18 2021.

Since the R community is generally pretty hot on making sure people use the latest version, out of date docs are much less valuable than current docs.

Please update to the latest versions