Consider removing reliance on RStudio

[multimeric]

Currently the lesson is a mix of R console functions like usethis::use_test, and RStudio utilities like "Build and Load Package". RStudio can't do everything whereas the console can, so there is an argument that it would be simpler to teach everything that way, and use functions like usethis::use_package() and devtools::build() instead of the RStudio utilities.

This would also make it easier to port to Positron, which seems like Carpentries is looking at.

[PabRod]

Hi there.

Some context might be useful here: the initiators of this lesson, @bvreede and I, had many conversations about this. Eventually, we decided to follow an intermediate approach... that probably is not fully satisfying for anyone 😅

One of our conclusions was that it can be very useful to use RStudio as a helper for learning the console commands. I suggest at least keeping the mention that RStudio buttons also print the command they call.