docs: add storage configuration guide

[baojun-zhang]

Description

add storage configuration guide

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

1. 更新了"storage"部分 ：

• 添加了根级配置参数说明
• 扩展了S3后端配置，包括详细的参数表和两种模式的配置示例（PathStyle和VirtualHostStyle）
• 完善了vectordb配置，添加了完整的参数表和volcengine vikingDB的配置示例

2. 修正了相关文档链接 ：更新了火山购买指南的链接路径。

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes