Detect and fail on misplaced files

[Weibye]

Action should not just ignore links in one of the target documents?

1. Document A has a link to a file that lies outside the scope.
2. The link is valid
3. The file exist
4. The action should detect that the file is misplaced
5. Report that it needs to be moved

So, how to detect that a file is misplaced and not just end up reporting any files that aren't even considered examples?

[Weibye]

Required by bevyengine/bevy#1650