feat(i18n): add locales

[lnquy065]

Hi, thank you for an awesome library.

Changes

This PR allows users to change the locale:

Here is an example:

const {TextRenderer} = require('@datadocs/rose-formatter')

const r1 = new TextRenderer('dddd, dd of mmmm of yyyy', 'vi')
console.log(r1.formatDate(
    new Date(2021, 7, 5, 14, 3, 9, 256)
))

• By default, the second parameter of TextRenderer will be 'en-us'.
• The locale format follows ISO 639-1 standard language codes.

Testing

• Added test/i18n.spec.js

Supported languages

• List of supported locales can be found in ./src/locales.js.

Note

I'm not sure if this PR affects performance, we can consider separating locales from the main package and letting users import them themselves.🍻