Add method to track upload progress

[sergeysova]

It is required to add a convenient method to track uploading progress.

const [uploadFx, progressChanged] = createUpload({
  baseUri: 'https://server.com',
})

progressChanged.watch(({params, progress}) => {
  if (progress.lengthComputable) {
    console.info(`Sent ${progress.loaded} of ${progress.total} bytes`)
  } else {
    console.log(`Sent ${progress.loaded} bytes`)
  }
})

uploadFx({path: '/upload/image', blob, name: 'demo.jpg'})