[i18n] Add Warning Banner for Outdated Non-English Documentation Pages

[caipeter888]

Description:

I noticed that several non-English documentation pages are outdated. For instance, the Chinese prerequisites page (https://tauri.app/zh-cn/start/prerequisites/#rust) is missing the "MSVC toolchain as default" warning. While using a machine that only has stable-x86_64-pc-windows-gnu installed, I repeatedly referred to the Chinese page and couldn’t figure out the compilation error issue until I switched to the English version of the documentation.

Proposal:

Could we add an automatic warning banner at the top of any translated pages that are known to be outdated? This banner would serve to alert readers that the translated content might be missing important updates, and they should refer to the English version for the most current information—similar to how untranslated pages currently display a notice like “This content is not available in your language.”

This improvement would help prevent confusion and save developers time by guiding them to the latest documentation when issues arise due to outdated translations.

Thank you for considering this proposal.