make notes more clear for upgrade-webpacker-v3-to-v4.md

Author: ihabadham

.github/markdown-link-check-config.json

@@ -23,6 +23,9 @@
     },
     {
       "pattern": "^https://github\\.com/shakacode/react-webpack-rails-tutorial/blob/master/client/webpack\\.client\\.base\\.config\\.js"
+    },
+    {
+      "pattern": "^https://github\\.com/shakacode/react_on_rails/tree/master/lib/install/config/"
     }
   ],
   "replacementPatterns": [

docs/additional-details/upgrade-webpacker-v3-to-v4.md

@@ -1,12 +1,12 @@
 # Upgrading rails/webpacker v3.5 to v4 (Outdated)
 
-_Note: This document is outdated. The configuration files referenced below were removed from React on Rails. For current configuration, see the [install generator templates](https://github.com/shakacode/react_on_rails/tree/master/lib/generators/react_on_rails/templates) or consider upgrading to [Shakapacker](https://github.com/shakacode/shakapacker)._
+_Note: This guide is outdated. The configuration files it references were removed when React on Rails moved to Shakapacker. For migrating from Webpacker to Shakapacker, see the Shakapacker guide to upgrading to [version 6](https://github.com/shakacode/shakapacker/blob/master/docs/v6_upgrade.md) and [version 7](https://github.com/shakacode/shakapacker/blob/master/docs/v7_upgrade.md)._
 
-The following steps could be followed to update a Webpacker v3.5 app to v4:
+The following steps can be followed to update a Webpacker v3.5 app to v4.
 
 1. Update the gem `webpacker` and the package `@rails/webpacker`
-1. Merge changes from the new default `.babelrc` to your `/.babelrc`. If you are using React, you need to add `"@babel/preset-react"`, to the list of `presets`.
-1. Copy the file `.browserslistrc` to `/`.
-1. Merge any differences between `config/webpacker.yml` and your `/config/webpacker.yml`.
+1. Merge changes from the new default [.babelrc](https://github.com/shakacode/react_on_rails/tree/master/lib/install/config/.babelrc) to your `/.babelrc`. If you are using React, you need to add `"@babel/preset-react"`, to the list of `presets`.
+1. Copy the file [.browserslistrc](https://github.com/shakacode/react_on_rails/tree/master/lib/install/config/.browserslistrc) to `/`.
+1. Merge any differences between [config/webpacker.yml](https://github.com/shakacode/react_on_rails/tree/master/lib/install/config/webpacker.yml) and your `/config/webpacker.yml`.
 
 Here is an [example commit of these changes](https://github.com/shakacode/react_on_rails-tutorial-v11/pull/1/files).