Include sample code in ADRG

[parmsam-pfizer]

Based on recent feedback from reviewers.

install.packages("datasetjson")
library(datasetjson)
dm <- read_dataset_json("dm.json")

[bms63]

Hey @copilot - can you add in a callout note in the the ADRG.qmd file that adds in a small snippet of reading in a datasetjson. The callout should be a information callout. Also, include a link to the R package - https://atorus-research.github.io/datasetjson/

https://quarto.org/docs/authoring/callouts.html