added workflows tests-with-R.yaml and tests-without-R.yaml to run tests with or without R packages, while ignoring R-dependent tests if R packages are not installed (tests-without-R.yaml)
I added a save-packages-R.yaml workflow to save R packages in the cache, so you don't have to install them every time you run a test (tests-with-R.yaml will take less time to run).
Separation of R and Python dependencies, by displaying warnings, in the case where a function that depends on an R package is run and R or the package are not installed. The warning asks you to install R if this is not the case and/or install the relevant R package if this is not the case.
CI part configuration:
Separation of R and Python dependencies, by displaying warnings, in the case where a function that depends on an R package is run and R or the package are not installed. The warning asks you to install R if this is not the case and/or install the relevant R package if this is not the case.