docs: Update internationalization.md

[oscarcala]

based on this answer https://github.com/hexojs/hexo/issues/1696#issuecomment-599218058 I propose to update the documentation as this is a FAQ.

Thanks

Check List

Please read and check followings before submitting a PR.

• [ ] I want to publish my theme on Hexo official website.
  • [ ] I have read the theme publishing doc.
  • [ ] name is unique.
  • [ ] link URL is correct.
  • [ ] preview URL is correct.
  • [ ] preview URL web site is rendered correctly.
  • [ ] Add a screenshot to source/themes/screenshots.
  • [ ] Screenshot filename is same as value of name.
  • [ ] Screenshot size is 800 * 500.
  • [ ] Screenshot file format is png.
• [ ] I want to publish my plugin on Hexo official website.
  • [ ] I have read the plugin publishing doc.
  • [ ] name is unique.
  • [ ] link URL is correct.
• [ X ] Others (Update, fix, translation, etc...)
  • Languages:
  • [ ] en English
  • [ ] ko Korean
  • [ ] pt-br Brazilian Portuguese
  • [ ] ru Russian
  • [ ] th Thai
  • [ ] zh-cn simplified Chinese
  • [ ] zh-tw traditional Chinese