As an end-user, I should be able to preview the attachment from form in form filling state

## What needs to be solved?
As an end user, I might have requirement to see the content of the attachment when I'm in form filling state

## How do you want it solved?
When a document is uploaded it should be possible to see the content live. Perhaps by mousehoover or a side window that opens.

## Alternative solutions

## Additional context

Start from the form-filling state and attachment upload flow; the issue does not identify files or tests. Clarify the preview interaction and supported attachment content before implementation, then verify that an uploaded document can be previewed live while the form is being filled.

Written by the indexing model from the issue text.