Add gRPC server example with file download

TestGrpc/Startup.cs

@@ -0,0 +1,26 @@
+using TestGrpc.Services;
+
+namespace TestGrpc;
+
+public class Startup
+{
+    public void ConfigureServices(IServiceCollection services)
+    {
+        services.AddGrpc(o => o.EnableDetailedErrors = true);
+    }
+
+    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
+    {
+        if (env.IsDevelopment())
+        {
+            app.UseDeveloperExceptionPage();
+        }
+
+        app.UseRouting();
+
+        app.UseEndpoints(endpoints =>
+        {
+            endpoints.MapGrpcService<GreeterService>();
+        });
+    }
+}