Add Triplicate States?

[mradamcox]

see GeoDaCenter/opioid-policy-scan#44 for original ticket from @Predict-This

Hello! Relatively simple and powerful addition to this resource would be to add a shapefile or simple dataset of Triplicate States. See https://academic.oup.com/qje/article-abstract/137/2/1139/6427381?redirectedFrom=fulltext&login=true for the powerful contribution of this program to prescription deterrence. "We find that OxyContin distribution was more than 50% lower in “triplicate states” in the years after OxyContin's launch."