[Feature] Internationalization (i18n) Support

[fangyinc]

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Hello. First off, thank you for the incredible work on chainlit. It has proven to be extremely valuable for our works.

As the user base for chainlit grows, there might be non-English speaking users who could benefit from using it. To make it more accessible to a global audience, I'd like to propose adding internationalization (i18n) support to chainlit.

Proposed Solution:

1. Integrate an i18n library/tool such as "react-i18next" to manage translations.
2. Refactor the existing codebase to make UI text elements translatable.
3. Add a language switcher to the UI, allowing users to select their preferred language.

I'm willing to help kickstart this process and contribute where necessary. Please let me know your thoughts, and if there's any way I can assist.

Although I'm not very knowledgeable about the frontend, I have tried implementing react-i18next in the current project. I've seen some preliminary positive results. I would be more than happy to contribute my code.

Thank you for considering this proposal.