Display attachment previews with extraction form for improved workflow when using projects

[HelenWDTK]

Currently, users need to switch between different pages or tabs to view attachments (like PDFs) and enter extracted data into the extraction form when using projects. This can be annoying, especially when extracting the answers to multiple questions. To streamline this workflow, we should display attachment previews directly alongside the sidebar with the form, allowing users to view the source document and input fields at the same time.

We could use something like PDF.js, or just display the sidebar to the existing html preview page.