Created by: heldinz
Verifies that the folders created during an eject (not just the files) do not exist. Exits with error if they do exist.
I tested this by creating scripts and config/jest folders in the app, then running npm run eject. The script failed early on both scripts and config, as expected. Removing these directories allowed the script to continue running and successfully create the required directories and copy the files over to them.
Closes #939 (closed).