hook up keyboard scrolling to Now Playing page tracklists

ui/browsing/nowplayingpage.go

@@ -262,6 +262,18 @@ func (a *NowPlayingPage) Route() controller.Route {
 	return controller.NowPlayingRoute("")
 }
 
+var _ Scrollable = (*NowPlayingPage)(nil)
+
+func (a *NowPlayingPage) Scroll(delta float32) {
+	switch a.tabs.SelectedIndex() {
+	case 0: /*play queue*/
+		a.queueList.Scroll(delta)
+	case 1: /*lyrics*/
+	case 2: /*related*/
+		a.relatedList.Scroll(delta)
+	}
+}
+
 var _ CanShowNowPlaying = (*NowPlayingPage)(nil)
 
 func (a *NowPlayingPage) OnSongChange(song mediaprovider.MediaItem, lastScrobbledIfAny *mediaprovider.Track) {

ui/widgets/playqueuelist.go

@@ -164,6 +164,10 @@ func (p *PlayQueueList) UnselectAll() {
 	p.list.Refresh()
 }
 
+func (p *PlayQueueList) Scroll(amount float32) {
+	p.list.ScrollToOffset(p.list.GetScrollOffset() + amount)
+}
+
 func (p *PlayQueueList) Refresh() {
 	p.list.EnableDragging = p.Reorderable
 	p.BaseWidget.Refresh()