Folder diff view

Thank you all for creating such a great extension! This has become my go-to tool for GitHub PR reviews. It's a much better alternative to the GitHub web interface in my opinion.

I'd like to suggest a feature that would significantly improve my workflow and potentially others' as well. The existing "Changes in Pull Request" unified diff view is an excellent way to quickly review changes across the entire PR. However, it would be incredibly helpful to have a folder-level unified diff view with the same layout.

Often during code reviews, certain folders contain many small, straightforward changes (e.g. such as during refactors or bulk updates) while others contain more involved changes. Currently, clicking through each individual file to review small changes is more cumbersome than scrolling through the consolidated PR diff view. However, since the existing unified view displays all files at once, it's hard to isolate just the easy-to-review files from the more complex ones.

The ideal solution would be to add a hover action or context menu to each folder in the file tree, allowing users to open a unified diff view that shows only the files within that folder. This would allow reviewers to quickly scroll through related changes, mark the entire folder as reviewed, and move on strategically.

Thank you again for the amazing work on this extension!

No files or tests are named. Start by locating the existing “Changes in Pull Request” unified diff view and the file-tree hover or context-menu actions. Done should include a folder action that opens a unified diff limited to that folder and supports marking the folder as reviewed.