chore(test-app): reconfigure so our babel.config.js gets picked

[tido64]

Description

Metro looks for a Babel config in projectRoot, which is currently set to ./src. Created a root index.js that imports ./src/index and removed projectRoot from server config.

Test plan

cd packages/test-app
yarn build --dependencies
yarn start

# In a separate terminal
curl -v 'http://localhost:8081/index.bundle?platform=ios'

[kelset]

it works