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

Beginne mit der Prüfung des bestehenden react-idle-Setups einschließlich seiner Tests, CI-Konfiguration, Beispiele, Flow-Nutzung sowie ESLint- und Rollup-Konfiguration. Vergleiche dieses Setup mit der vorgeschlagenen create-react-app-style CLI und entscheide, ob das Scaffold in dieses Repository oder in ein separates Repository gehört. Als abgeschlossen gilt die Aufgabe, wenn das unterstützte Scaffold, die CI-Wahl und der Umfang der wiederverwendbaren Defaults klar definiert sind.