[Documentation enhancement] demonstrate a way to upload a local file in js

[3aluw]

The JS examples on uploading a file aren't coherent, and they don't provide a clue for the most important use case (which is uploading local files)
the upload example gives a way to upload a simple inline SVG

  file: {
      'en-US': {
        contentType: 'image/svg+xml',
        fileName: 'circle.svg',
        file: '<svg><path fill="red" d="M50 50h150v50H50z"/></svg>'
      }

creating an asset example shows how to create an asset based on a url :

  file: {
      'en-US': {
        contentType: 'image/jpeg',
        fileName: 'example.jpeg',
        upload: 'https://example.com/example.jpg'
      }

Although direct uploads are supported since 2017 (as I guess) there is no example on the documentation, This causes some confusion as in this post or on stack overflow

[hnrq]

I don't have a single clue on how to upload a local image. There is an example using the Plain API, but the file just hangs in processing forever. I have tried sending a Buffer, sending a fs.readFileSync().toString(), or even the new ArrayBuffer(file.length)` thing (Which doesn't make sense to me, even though it's what's in the example). How can I upload an image using this?