amazon link and instructions for mobile users

Author: trevorcampbell

index.Rmd

@@ -37,8 +37,12 @@ output:
 # Welcome! {-}
 
 This is the [website](https://datasciencebook.ca/) for *Data Science: A First Introduction*. 
+You can read the web version of the book on this site. Click a section in the table of contents
+on the left side of the page to navigate to it. If you are on a mobile device,
+you may need to open the table of contents first by clicking the menu button on 
+the top left of the page.
 You can purchase a PDF or print copy of the book 
-on the [CRC Press website](https://www.routledge.com/Data-Science-A-First-Introduction/Timbers-Campbell-Lee/p/book/9780367524685).
+on the [CRC Press website](https://www.routledge.com/Data-Science-A-First-Introduction/Timbers-Campbell-Lee/p/book/9780367524685) or on [Amazon](https://www.amazon.com/Data-Science-First-Introduction-Chapman/dp/0367532174/ref=sr_[…]qid=1644637450&sprefix=data+science+timber%2Caps%2C166&sr=8-1).
 
 ```{r bookcover, echo = FALSE, fig.retina = 2, out.width = "45%"}
 knitr::include_graphics("img/ds-a-first-intro-cover.jpg")