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

首先审查现有的 react-idle 设置，包括其测试、CI 配置、示例、Flow 的使用，以及 ESLint 和 Rollup 配置。将该设置与提议的 create-react-app-style CLI 进行比较，并决定 scaffold 应属于此 repository 还是单独的 repository。明确支持的 scaffold、CI 选择以及可复用默认值的范围，即表示完成。