Display files output in form playground

[vsgoulart]

What should we do?

On #1239 we introduce the filepicker component. This added the files to the submit event which contains a map with all the files used in the form.

The correlation of this files to each is done via a key (which is present in data output)
For example

// My data JSON output
{
  "myInvoicesPDFs": "files::f4l4c3lw8qwinypvjn2p1enkl"
}

form.on("submit", ({data, files}) => {
  const myInvoicesPDFs = files.get(data.myInvoicesPDFs)

  // now I have an array with all PDFs
})

Because only "myInvoicesPDFs": "files::f4l4c3lw8qwinypvjn2p1enkl" is visible on the form output users get confused because they don't get the whole picture.

To fix that we could create a new file view or tab in the form output so the users can easily link the JSON output to the file output

Why should we do it?

To reduce confusion when handling files in form-js