Return IServiceCollection from AddDirectoryBrowser extension methods

Author: javiercn

src/Microsoft.AspNetCore.StaticFiles/DirectoryBrowserServiceExtensions.cs

@@ -14,14 +14,17 @@ public static class DirectoryBrowserServiceExtensions
         /// Adds directory browser middleware services.
         /// </summary>
         /// <param name="services">The <see cref="IServiceCollection" /> to add services to.</param>
-        public static void AddDirectoryBrowser(this IServiceCollection services)
+        /// <returns>The <see cref="IServiceCollection"/> so that additional calls can be chained.</returns>
+        public static IServiceCollection AddDirectoryBrowser(this IServiceCollection services)
         {
             if (services == null)
             {
                 throw new ArgumentNullException(nameof(services));
             }
 
             services.AddWebEncoders();
+
+            return services;
         }
     }
 }