Upload组件如何加boundary

[giveMeFiveoo]

Issue Type:

• [ ] Bug
• [ ] Feature
• [x] Help

Version & Environment:
版本: 0.7.0

Description: RquestHeaders 并没有出现类似于 Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryenX707C2TPy3TNdE