blob.textStream()
返回一个新的 ReadableStream，允许将 Blob 的内容作为 UTF-8 解码字符串流来读取。这相当于将 blob.stream() 通过一个用 UTF-8 设置的 TextDecoderStream 管道传输。
🌐 Returns a new ReadableStream that allows the content of the Blob to be read
as a stream of UTF-8 decoded strings. It is equivalent to piping
blob.stream() through a TextDecoderStream set up with UTF-8.