Add gRPC server example with file download

TestGrpc/Program.cs

@@ -0,0 +1,16 @@
+namespace TestGrpc;
+
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        CreateHostBuilder(args).Build().Run();
+    }
+
+    public static IHostBuilder CreateHostBuilder(string[] args) =>
+        Host.CreateDefaultBuilder(args)
+            .ConfigureWebHostDefaults(webBuilder =>
+            {
+                webBuilder.UseStartup<Startup>();
+            });
+}