T3182

Add header to code files in e.cash directory using next.js default settings

Note: Diffs planned after this to (1) fix known lint error about next/babel and to (2) expand lint dirs; right now, eslint is only linting nextjs default folders

Ref: https://nextjs.org/docs/pages/building-your-application/configuring/eslint

Confirm the app still builds (lint errors will throw an error during build)

npm run lint and no errors

npm test