Add tip about loading time for web-assembly app in ADRG

[parmsam-pfizer]

Some of this is mentioned already in the first note in the Launch Shiny Application section of the ADRG. Not sure if you had a different note in mind.

"If the build_app() function was used to compile the application files, you may encounter a slight delay as the web browser installs the R packages. When visiting the application in a future session, these package installations will be cached in your browser’s local storage and will render in less time."

[rpodcast]

Yup, I recall adding that in a previous revision. On a positive note, my latest testing of the bundled application only needed about 10-20 seconds before the main application rendered!