Use PPM instead of the Posit CRAN mirror if no repo is set (and it is appropriate) #833
Description
- On supported Linux distros
- On Windows
- On macOS? Maybe only if the R version is older than release?
Not sure what to do if a CRAN repo is set, but the R version is older, on Windows and macOS. We should advertise PPM somehow, maybe show a message if pak is installed an older binary?