Core: Signal duplicated editors

FakeVim needs some notification even in cases where the
duplication is triggered outside the EditorManager as in
QmlDesigner's qml-editor.

Fixes: QTCREATORBUG-22344
Change-Id: Ia4950ff4b02d3f89779f03ff4c106a07ccff2106
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/imageviewer/imageviewer.cpp

@@ -189,6 +189,9 @@ Core::IEditor *ImageViewer::duplicate()
     other->d->imageView->createScene();
     other->updateToolButtons();
     other->d->ui_toolbar.labelImageSize->setText(d->ui_toolbar.labelImageSize->text());
+
+    emit editorDuplicated(other);
+
     return other;
 }