2024-08-30: Internationalization support for the UI

There is now an optional feature to enable a language picker in the UI:
https://github.com/Azure-Samples/azure-search-openai-demo/blob/main/docs/deploy_features.md#enabling-language-picker
This will change the language of UI messages, but not affect anything about the LLM system prompt.

Screenshot: 

As a result of this PR, all text messages for the UI are now in single files, per language, and all messages can be edited in one place. See guide here: https://github.com/Azure-Samples/azure-search-openai-demo/blob/main/docs/customization.md#customizing-the-ui

What's Changed

• Reduce JS size by using more specific import for react-syntax-highlighter by @pamelafox in #1947
• Send down LLM messages as dictionaries in thought process by @pamelafox in #1948
• Frontend multi-language support #1690 by @bnodir in #1790

New Contributors

• @bnodir made their first contribution in #1790

Full Changelog: 2024-08-23...2024-08-30