docs: document and internationalize multi-provider JWT integration

- Add comprehensive documentation describing how to support multiple JWT providers (such as Azure AD and internal authentication) to the guide
- Provide a step-by-step implementation, including dynamic token validation using KeyFunc, helper functions, and multi-provider route setup
- Include production-ready Azure AD integration examples, with key rotation and claim validation details
- Summarize common issues when handling tokens from several providers and suggest solutions such as claim normalization and error handling improvements
- Add alternative middleware chaining approaches for even more advanced use cases
- Offer key considerations and reference resources for implementing robust multi-provider JWT support
- Translate all new multi-provider documentation to Simplified Chinese and Traditional Chinese guides with detailed code examples and strategies

fix #283

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Author: appleboy