Core plugin outline integration with the new PDF viewer

Use case or problem

Core plugin outline integration with the new PDF viewer.
Outline core plugin and PDF viewer’s outline appearances are very similar. In order to see the outline of current file, instead of jumping back and forth between the outline plugin for regular notes, and new PDF viewer’s table of contents view for PDFs, it would be a lot more convenient to see the outline in one place (the core plugin) regardless whether you’re in a PDF or a regular note.

Proposed solution

Core plugin outline would work the same for regular notes, but when you open a PDF, instead of showing “No headings found.” It would display the outline, the same way it’s displayed in PDF viewer’s table of contents view.