Creating Documention for psborrow2

Because psborrow2 relies on (CmdStan)[https://mc-stan.org/users/interfaces/cmdstan], which is a shell interface to Stan missing from CRAN’s system dependencies, vignettes are pre-knitted and included in the package.

If you are making a new vignette or are proposing changes to an existing vignette, first build the package locally (devtools::build()), install the package (e.g., install.packages("path/to/local/package.tar.gz", repos = NULL)), and then make changes to the vignette in the vignettes/original directory.

Then use the Make target build to build the vignettes. See vignettes/Makefile for other targets.