simplify GraphQL files loading

Created by: mrduguo

use simpler graphql-tag/loader other than graphql.macro

Document updated as well. You may see how it was looks before and after:

The implementation has been published as graphql-tag-react-scripts@5.0.2

Manual test for none GraphQL project

npx create-react-app none-gql-project --scripts-version graphql-tag-react-scripts@5.0.2
cd none-gql-project
npm run build
# expected build success without error

Manual test for Apollo based GraphQL project

npx create-react-app apollo-gql-project --scripts-version graphql-tag-react-scripts@5.0.2
cd apollo-gql-project
npm install --save @apollo/client
cat <<EOT > src/index.js
import query from './foo.graphql';
console.log(query)
EOT

cat <<EOT > src/foo.graphql
query {
  hello {
    world
  }
}
EOT

npm run build
grep hello build/static/js/main.*.js

# expect contain the hello keyword