I also added a warning about r_version_35 which should not be used anymore if we have 3 distinct version of R to install
from the ubuntu cran repository.
Note that if you set r_version to '40', it mean you're on a recent ubuntu and so you will have r_version_35 auto setted to true, so the other check of this variable will still work.
Add R 4 install from cran repository.
I also added a warning about r_version_35 which should not be used anymore if we have 3 distinct version of R to install from the ubuntu cran repository.
Note that if you set r_version to '40', it mean you're on a recent ubuntu and so you will have r_version_35 auto setted to true, so the other check of this variable will still work.
Maybe we should set the default version to 35 now, as nobody use the 34 anymore, you can check here https://cran.r-project.org/bin/linux/ubuntu/README.html and see that it is only available on very old ubuntu.