First working version with devise+rails_admin

app/javascript/packs/application.js

@@ -7,7 +7,8 @@ require("@rails/ujs").start()
 require("turbolinks").start()
 require("@rails/activestorage").start()
 require("channels")
-
+global.toastr = require("toastr")
+import "../stylesheets/application"
 
 // Uncomment to copy all static images under ../images to the output folder and reference
 // them with the image_pack_tag helper in views (e.g <%= image_pack_tag 'rails.png' %>)

app/javascript/stylesheets/application.scss

@@ -0,0 +1 @@
+@import 'toastr'