How to make a shiny or javascript alert that appears in front of other windows/apps-CodePudding

I am writing an app that will be used to copy large numbers of photos (often tens of thousands at a time) from SD cards to external hard drives, which people will be running in the background while they do other work. I want to notify the user when the file copying is finished so they don't have to keep checking the app. I have used shinyalert() in the past, and I am also aware of using javascript functions to send alerts as well (this is the one I found:

$( document ).ready(function() {
  Shiny.addCustomMessageHandler('alert', function(message) {
    alert(message)
  })
});

). But, those only appear when the app is open, and I want something that will pop up in front of any other windows. My solution was to use system2() to call a powershell script, which I borrowed from this page:

When it is displayed on Linux, Windows maybe a little different, but still should be above all programs.