Create Makefile target to properly run R CMD build with r-devel

[apulsipher]

Currently, running R CMD build in the epiworldR container results in NOTEs when submitting to CRAN because the Authors field in the DESCRIPTION files is generated incorrectly. R CMD build needs to be run on r-devel, instead. If we add a Makefile target for this, we can simplify the developer effort needed to spin up a separate container with r-devel and build from there.

[apulsipher]

Alternatively, the GHA for R CMD check already builds with R-devel. We can use the uploaded artifact, but note that it is a zip file titled epiworldR-built-package-ubuntu-latest-devel.zip which contains the epiworldR_0.6.0.0.tar.gz file. We need to upload the tar.gz file, so we need to unzip the .zip. On macOS, I found that simply unzipping the usual way causes macOS to unzip both files immediately, but if I use the unzip terminal command, I can unzip just the first layer and get the tar.gz file for submission.

[apulsipher]

Add the above comment to documentation, rather than as a separate workflow, after the current (v0.6.0.0) CRAN submission is finished.