[e.cash] Expand scope of linter to include other files and directories that should be linted

Summary:
Depends on D14077

Add 'data' and 'styles' folders to eslint on top of nextjs default directories

Add top level files .eslintrc.js, next.config.js, and jest.config.js

Test Plan:
@bot preview-e.cash still builds
npm run lint and no errors

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D14078