Visibility into app startup errors from IIS

[mwiseley-wakefly]

I did a recent deployment to Umbraco Cloud with a Production web.config transformation that resulted in a validation error in the web.config, taking down the Live site. The site served 500 status without any detail, and there was nothing indicating the issue in either the Umbraco trace logs via Kudu or the log messages shown in the Cloud dashboard. On a server, IIS reports an issue like this in the Windows Event Viewer Application log. It would avoid a lot of guesswork to have visibility into this kind of error in Umbraco Cloud.