imageView: Add only viewed images to recently used

Only adding images expclicitly opened via file browser
or drag and drop. Do not add images while browsing
SlidingView to avoid spamming recently used files.

Closes #53

src/widgets/image_page.rs

@@ -153,10 +153,6 @@ impl LpImagePage {
 
         obj.imp().image.set_file(&file);
 
-        // This doesn't work properly for items not explicitly selected
-        // via the file chooser portal. I'm not sure how to make this work.
-        gtk::RecentManager::default().add_item(&file.uri());
-
         spawn!(clone!(@weak obj, @strong path => async move {
             let imp = obj.imp();
             imp.image.load(&path).await;