feat: cross platform projects.

demo/Ursa.Demo.Browser/Program.cs

@@ -0,0 +1,17 @@
+using System.Runtime.Versioning;
+using System.Threading.Tasks;
+using Avalonia;
+using Avalonia.Browser;
+
+[assembly: SupportedOSPlatform("browser")]
+
+namespace Ursa.Demo.Browser;
+
+internal partial class Program
+{
+    private static async Task Main(string[] args) => await BuildAvaloniaApp()
+        .StartBrowserAppAsync("out");
+
+    public static AppBuilder BuildAvaloniaApp()
+        => AppBuilder.Configure<App>();
+}