feat(guides) Update service worker docs (#3091)

* add: with correct diff formatting

* fixes: PR review update note, remove diff

Author: benschac

src/content/guides/progressive-web-application.md

@@ -5,6 +5,7 @@ contributors:
   - johnnyreilly
   - chenxsan
   - EugeneHlushko
+  - benschac
 ---
 
 T> This guide extends on code examples found in the [Output Management](/guides/output-management) guide.
@@ -34,6 +35,8 @@ __package.json__
 }
 ```
 
+Note: [webpack DevServer](/configuration/dev-server/) writes in-memory by default. We'll need to enable [writeToDisk](/configuration/dev-server#devserverwritetodisk-) option in order for http-server to be able to serve files from `./dist` directory.
+
 If you haven't previously done so, run the command `npm run build` to build your project. Then run the command `npm start`. This should produce the following output:
 
 ``` bash