applets/devicenotifier: forward keys to `ListView`

So pressing arrow keys can navigate in the applet.

applets/devicenotifier/package/contents/ui/FullRepresentation.qml

@@ -29,6 +29,8 @@ PlasmaExtras.Representation {
 
     collapseMarginsHint: true
 
+    Keys.forwardTo: [notifierDialog]
+
     header: PlasmaExtras.PlasmoidHeading {
         visible: !(Plasmoid.containmentDisplayHints & PlasmaCore.Types.ContainmentDrawsPlasmoidHeading) && devicenotifier.mountedRemovables > 1
         PlasmaComponents3.ToolButton {
@@ -166,6 +168,11 @@ PlasmaExtras.Representation {
                 }
             }
 
+            Keys.onDownPressed: {
+                notifierDialog.incrementCurrentIndex();
+                notifierDialog.currentItem.forceActiveFocus();
+            }
+
             Loader {
                 anchors.centerIn: parent
                 width: parent.width - (PlasmaCore.Units.largeSpacing * 4)