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

まず、テスト、CI 設定、例、Flow の使用、および ESLint と Rollup の設定を含む、既存の react-idle のセットアップを確認します。そのセットアップを、提案されている create-react-app-style CLI と比較し、scaffold をこの repository に置くべきか、別の repository に置くべきかを決定します。サポート対象の scaffold、CI の選択、および再利用可能なデフォルトの範囲が明確に定義されれば完了です。