For “Maintaining R”, would it be worth adding architecture-specific R_LIBS_USER paths?

[batpigandme]

I'm not sure whether or not this is obscure, or what many people are moving to/have set up with tools like RSwitch, rcli, and r-lib/rim, but, these days my M1 Mac user library paths look different to what they did in the last pass on the Maintaining R chapter (below)

what-they-forgot/13_maintaining-r.Rmd

Lines 79 to 91 in 9b3d43c

	Once this is setup, the process for transferring your package library becomes.
	(assumes `R_LIBS_USER` is set to `~/Library/R/3.5/library`).
	```r
	# Install new version of R (lets say 3.5.0 in this example)
	# Create a new directory for the version of R
	fs::dir_create("~/Library/R/3.5/library")
	# Re-start R so the .libPaths are updated
	# Lookup what packages were in your old package library
	pkgs <- fs::path_file(fs::dir_ls("~/Library/R/3.4/library"))

e.g. My default setup for R_LIBS_USER is now ~/Library/R/arm64/4.2/library, with the previous version for this architecture at ~/Library/R/arm64/4.1/library.

However, I also have ~/Library/R/x86_64/4.2/library and ~/Library/R/x86_64/4.1/library.

Again, not sure how common this is/will become, but, let me know if you think it'd be worth a PR.