文件(或文件)上传的loopback-component-storage doc说：
loopback documentation

描述：

Upload one or more files into the specified container. The request
body must use multipart/form-data which the file input type for HTML
uses.

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方法：

upload(req,res,cb)

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REST URI：

POST
/api/containers/:container/upload

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有人请展示如何在Angular / Javascript中创建此multipart / form请求的示例吗？