Leprechaun is not yet on CRAN, get it from Github.
# install.packages("remotes")
::install_github("devOpifex/leprechaun") remotes
From the root of a package scaffold a leprechaun application.
::create_package("myApp")
usethis::scaffold() leprechaun
This effectively generates code within the package to run a shiny application within a package: leprechaun does not become a dependency to your project.