* 📚 add doc for the trends API.
---------
* 📚 添加 trends api 相关文档
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **Documentation**
- Added sections for `[Token]` and `[Trend]` in the Registry API
documentation.
- Introduced a new endpoint `GET /downloads/range/:start::end/:pkgName`
for fetching package download trends.
- Included sample response data for the `Trend` endpoint.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
