cra-to-parcel

This script migrates a non-ejected Create React App to Parcel.

``sh
npx cra-to-parcel
`

What is migrated?

For full details and manual instructions, see the Parcel website. In summary:

1. react-scripts is replaced with parcel in dependencies and package.json scripts
2. Jest config is ejected, and the necessary dependencies are installed
3. public/index.html is updated to use Parcel syntax, and add explicit