Added elmah.io to Analytics and Error Reporting

elmah.io offers a free plan for open-source developers. Details in the link provided.

Author: ThomasArdal

dotnet-free-oss-services.md

@@ -42,6 +42,7 @@ Please sort projects alphabetically and provide a one-line description. Where po
 
 ## Analytics and Error Reporting
 
+* [elmah.io](https://elmah.io/sponsorship/opensource/) - Error logging and uptime monitoring for .NET.
 * [Bugsnag](https://bugsnag.com/blog/bugsnag-loves-open-source) - Cross platform error reporting.
 * [Sentry](https://sentry.io/for/open-source/) - Cross platform error reporting.