Document Jest usage

[0pdd]

The puzzle 1484-a3f3427b from #1484 has to be resolved:

mystamps/src/main/frontend/jest.config.js

Line 1 in bacab7b

// @todo #1484 Document Jest usage

The puzzle was created by Slava Semushin on 10-Jan-21.

[php-coder]

Checklist:

• update README.md

[php-coder]

Useful links:

• https://jestjs.io
• https://jestjs.io/docs/en/api Jest functions
• https://jestjs.io/docs/en/expect Jest expect() standard matchers
• https://github.com/testing-library/react-testing-library
• https://github.com/testing-library/jest-dom
• https://github.com/testing-library/jest-dom#table-of-contents (a list of matchers)
• https://github.com/testing-library/user-event
• https://github.com/mswjs/msw
• https://testing-library.com/docs/react-testing-library/example-intro/
• List of aria roles: https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles
• https://github.com/A11yance/aria-query (used by react-testing-library under the hood)
• https://www.newline.co/@dmitryrogozhny/how-to-start-using-react-testing-library--0e7695e8