It appears the only help resource for authoring runtime: shiny_prerendered documents (https://rmarkdown.rstudio.com/authoring_shiny_prerendered.html) is now gone. The link now redirects to the R markdown book which does not contain any documentation about the shiny_prerendered runtime (i.e., the different contexts and what paths are to be used for resources). There is no other documentation about this runtime available, except for the source code.
Is the runtime silently phased out? This would be good to know to avoid using it for new projects or webpages.
Thanks!