Add to support all translated text in one file better for GitHub Copilot

[huacnlee]

For example:

welcome:
  en: Welcome to use Rust I18n.
  zh-CN: 欢迎使用 Rust I18n.
  zh-HK: 歡迎使用 Rust I18n.
login:
  en: Login
  zh-CN: 登录
  zh-HK: 登入

After that, when we write en, the GitHub Copilot or other AI tool will give us a suggestion of other translations.

And we need to support both translation's struct.