Update README with link to vignettes for setup

Author: jgabry

README.md

@@ -4,6 +4,6 @@ Built in the vein of [stan-dev/quarto-config](https://github.com/stan-dev/quarto
 
 Styling for Stan sites built with pkgdown. Do not use this theme in a non-Stan package.
 
-See the vignettes for setup instructions.
+See the [vignettes](https://mc-stan.org/pkgdown-config/articles/) for setup instructions.
 
 For any further concerns or help, open an issue and/or ping `@Visruth` on the Stan Slack.