Add App.module.css instead of App.css on project initialization

Created by: esvyridov

The idea behind this change is to show how CSS Modules works in CRA.

In the end a new project shows how to import a regular stylesheet in the index.js and how to import CSS Module.

This change came in my mind after this thread: https://twitter.com/dan_abramov/status/1195440508681646080?s=20