Highlight changed images

Can we post some screenshots of the before/after?

Here's how it looks:

Seems like a relatively helpful change.

Pipeline is failing.

Odd - the test failures relate to PHP code sniffer issues in files that aren't being changed - this change is only a CSS change.

Have merged 2.x into this branch and pushed.

This is looking good, however I don't think we should add the padding to non img diffs. I've added a :has selector to fix that. Here's what it looks like now: