Update 3.0-upgrade-notes.md

docs/3.0-upgrade-notes.md

@@ -36,7 +36,7 @@
 - Copy these files from example repo
 	- `app/ErrorPage.elm`
 	- `app/Effect.elm`
-- `elm-pages add` is replaced by `elm-pages codegen`
+- `elm-pages add` is replaced by `elm-pages run` for running custom scripts - by convention a script/src/AddRoute.elm script is used for scaffolding a new route.
 - `elm-pages codegen` command (to create generated files, helpful for build servers) is renamed to `elm-pages gen`
 - Route modules exposed value defining the route used to be called `page`, now needs to be `route`
 - In `Route.link` function, the `Route` used to be the first argument, it is now the last argument (works nicely if you pipe the Route in as an argument).