Migrate to Avalonia (#1220)

DiscordChatExporter.Gui/Utils/NativeMethods.cs

@@ -0,0 +1,12 @@
+using System.Runtime.InteropServices;
+
+namespace DiscordChatExporter.Gui.Utils;
+
+internal static class NativeMethods
+{
+    public static class Windows
+    {
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern int MessageBox(nint hWnd, string text, string caption, uint type);
+    }
+}