Update README.md

Author: kevinchalet

README.md

@@ -13,17 +13,16 @@ AspNet.Security.OpenId.Providers
 **Adding external authentication to your application is a breeze** and just requires a few lines in your `Startup` class:
 
 ```csharp
-// Add Steam authentication support.
-app.UseSteamAuthentication();
-
-// Add StackExchange authentication support.
-app.UseOpenIdAuthentication(options =>
+public void ConfigureServices(IServiceCollection services)
 {
-    options.AuthenticationScheme = "StackExchange";
-    options.DisplayName = "StackExchange";
-    options.Authority = new Uri("https://openid.stackexchange.com/");
-    options.CallbackPath = "/signin-stackexchange";
-});
+    services.AddAuthentication()
+        .UseSteam()
+        .UseOpenId("StackExchange", "StackExchange", options =>
+        {
+            options.Authority = new Uri("https://openid.stackexchange.com/");
+            options.CallbackPath = "/signin-stackexchange";
+        });
+}
 ```
 
 See [https://github.com/aspnet-contrib/AspNet.Security.OpenId.Providers/tree/dev/samples/Mvc.Client](https://github.com/aspnet-contrib/AspNet.Security.OpenId.Providers/tree/dev/samples/Mvc.Client) for a complete sample **using ASP.NET Core MVC and supporting multiple external providers**.