Update window title when changing selection in comparison mode
The window title now updates with the currently selected image when the user changes the selection in comparison mode.
View and select different images with and without comparison mode and verify the title.
Resize images by resizing the window or selecting/deselecting images while in comparison mode and verify the title.
View and switch between images in normal mode to verify it still works, including title updates.
Reviewers: Gwenview, ngraham, rkflx
Reviewed By: Gwenview, ngraham, rkflx
Subscribers: muhlenpfordt, ngraham, rkflx, Gwenview
Differential Revision: https://phabricator.kde.org/D11105