Add example with internationalization

[einatnielsen]

internationalization and localization are means of adapting application to different languages. in context to front-end development it could be internal implementation or 3rd party package. However, In terms of testing we want to explain what're the guidelines to test i18n case.

usually i18n implementation is key/value map for each language, which means inside components we use keys to render reach static text instead of write the actual text. for example:

without i18n:<div>hello world </div>
with I18n: <div>formatMessage('examples.hello.world')</div>

References
https://testing-library.com/docs/example-react-intl