Update R4DS mention. (#256)

Thank you so much for the mention! If it's ok, I'd love to use our updated name, and link to the book club slides on this online version!

index.qmd

@@ -26,7 +26,7 @@ He occasionally blogs about data, management, and leadership at:
 Thank you to current and former members of the Solutions Engineering
 team at Posit, who taught me most of what's in this book.
 
-Huge thanks to the R4DS book club, especially Jon Harmon, Gus Lipkin,
+Huge thanks to the [DSLC book club](https://dslc.io/do4ds), especially Jon Harmon, Gus Lipkin,
 and Tinashe Michael Tapera, who read an early (and rough!) copy of this
 book and gave me amazing feedback.