13 Documenting the package and adding README and pkgdown website

At build time we generate the package’s reference documentation, README, and pkgdown website: litr::document() writes the man/ pages and NAMESPACE; the README is rendered from source-files/README.Rmd (its two figures copied into man/figures/); the CITATION file is installed so citation("cssr") and the pkgdown “Citation” page cite the paper (arXiv:2201.00494); the Prediction and Advanced usage vignettes are added from source-files/ via litr::add_vignettes(); and litr::add_pkgdown() builds the site (including the vignettes under Articles).