6_0_upgrade.md in webpacker-6.0.0.beta.4 vs 6_0_upgrade.md in webpacker-6.0.0.beta.5

@@ -28,21 +28,35 @@
 
   ```bash
   bundle exec rails webpacker:install
   ```
 
-- Change `javascript_pack_tag` and `stylesheet_pack_tag` to `javascript_packs_with_chunks_tag` and
-  `stylesheet_packs_with_chunks_tag`
+- Change `javascript_packs_with_chunks_tag` and `stylesheet_packs_with_chunks_tag` to `javascript_pack_tag` and
+  `stylesheet_pack_tag`.
 
 7. If you are using any integrations like `css`, `React` or `TypeScript`. Please see https://github.com/rails/webpacker#integrations section on how they work in v6.0.
 
 8. Copy over any custom webpack config from `config/webpack_old`
 
+- Common code previously called 'environment' changed to 'base' 
+- import `environment` changed name to `webpackConfig`.
+
   ```js
   // config/webpack/base.js
   const { webpackConfig, merge } = require('@rails/webpacker')
   const customConfig = require('./custom')
 
   module.exports = merge(webpackConfig, customConfig)
   ```
 
 9. Copy over custom browserlist config from `.browserlistrc` if it exists into the `"browserlist"` key in `package.json` and remove `.browserslistrc`.
+
+10. `extensions` was removed from the webpacker.yml file. Move custom extensions to
+  your configuration by by merging an object like this. For more details, see docs for 
+  [Webpack Configuration](https://github.com/rails/webpacker/blob/master/README.md#webpack-configuration)
+```js
+{
+  resolve: {
+      extensions: ['.ts', '.tsx']
+  }
+}
+```