Added playlist view and initial playlist view logic.

Harmonia.UI/Views/PlaybackBar.axaml.cs

@@ -45,4 +45,16 @@ public partial class PlaybackBar : UserControl
         _viewModel.CurrentPosition = slider.Value;
         _viewModel.IsPositionChangeInProgress = false;
     }
+
+    private void VolumeSlider_PointerWheelChanged(object? sender, PointerWheelEventArgs e)
+    {
+        double mouseWheelDelta = e.Delta.Y;
+
+        if (mouseWheelDelta == 0)
+            return;
+
+        double delta = mouseWheelDelta > 0 ? .02 : -.02;
+
+        _viewModel.Volume += delta;
+    }
 }