fix rare intermittent "CGI application encountered an error" errors

docs/release-notes.md

@@ -7,6 +7,7 @@
 
 * For the web UI:
   * Updated the JSON validator and Content Patcher schema for Content Patcher 1.13.
+  * Fixed rare intermittent "CGI application encountered an error" errors.
 
 * For modders:
   * Fixed asset propagation on Linux/Mac for monster sprites, NPC dialogue, and NPC schedules.

src/SMAPI.Web/Program.cs

@@ -18,6 +18,7 @@ namespace StardewModdingAPI.Web
                 .CreateDefaultBuilder(args)
                 .CaptureStartupErrors(true)
                 .UseSetting("detailedErrors", "true")
+                .UseKestrel().UseIISIntegration() // must be used together; fixes intermittent errors on Azure: https://stackoverflow.com/a/38312175/262123
                 .UseStartup<Startup>()
                 .Build()
                 .Run();