CLI could initialize the scaffolding for releasing React libs

Description

Releasing open source React components requires heavy scaffolding. Once we are done with tests, CI, and examples for react-idle, we could use that setup for other similar projects

React Idle setup is somewhat opinionated but to a reasonable degree. For instance:

• Flow is set up. Not all projects require flow, but having type safety in an open source project is extremely helpful
• code formatting with eslint and prettier should stay there, but tweaks are possible
• rollup is used over webpack, which may introduce a learning curve. Still, rollup has certain advantages for libraries, which was also heavily researched by React team
• testing suite may prove to be too specific, but we'll see that it's reasonable enough
• we like to work with different CIs and will need to pick one

This may require a separate repo. It would be interesting to create something like create-react-app so it can be maintained from one place

Start by reviewing the existing react-idle setup, including its tests, CI configuration, examples, Flow usage, ESLint and Rollup configuration. Compare that setup with the proposed create-react-app-style CLI and decide whether the scaffold belongs in this repository or a separate one. Done means the supported scaffold, CI choice, and scope of reusable defaults are clearly defined.