create kestrel server for serving static files

util/Server/Startup.cs

@@ -0,0 +1,16 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Server
+{
+    public class Startup
+    {
+        public void ConfigureServices(IServiceCollection services)
+        { }
+
+        public void Configure(IApplicationBuilder app)
+        {
+            app.UseFileServer();
+        }
+    }
+}