Added WinUI project.

Harmonia.WinUI/Converters/ArtistsToStringConverter.cs

@@ -0,0 +1,26 @@
+using Microsoft.UI.Xaml.Data;
+using System;
+using System.Collections.Generic;
+
+namespace Harmonia.WinUI.Converters;
+
+public partial class ArtistsToStringConverter : IValueConverter
+{
+    public ArtistsToStringConverter()
+    {
+
+    }
+
+    public object Convert(object value, Type targetType, object parameter, string language)
+    {
+        if (value is not string[] artists)
+            return string.Empty;
+
+        return string.Join(" / ", artists);
+    }
+
+    public object ConvertBack(object value, Type targetType, object parameter, string language)
+    {
+        throw new NotImplementedException();
+    }
+}