"publishing.html" documentation article has mis-rendered R code blocks

[rcarboni]

In the R Markdown section: https://rstudio.github.io/r2d3/articles/publishing.html#r-markdown

R code windows are not rendering correctly on the pkgdown website (i.e. where it's trying to include the Rmarkdown headers within an R code block). There might be something breaking with the number of backticks.