Add swagger-stats to the list of Other utilities (#840)

Propose to add [swagger-stats](https://github.com/slanatech/swagger-stats) to the list of Other third-party utilities. swagger-stats is node.js module that exposes Prometheus metrics for REST API in node.js app.

content/docs/instrumenting/exporters.md

@@ -193,3 +193,5 @@ practices.
    * Go: [prombolt](https://github.com/mdlayher/prombolt)
    * Java/JVM: [Hystrix metrics publisher](https://github.com/ahus1/prometheus-hystrix)
    * Python-Django: [django-prometheus](https://github.com/korfuri/django-prometheus)
+   * Node.js: [swagger-stats](https://github.com/slanatech/swagger-stats)
+