add comments about monitoring on the main backend services page

src/content/docs/en/guides/backend.mdx

@@ -5,7 +5,7 @@ i18nReady: true
 ---
 import BackendGuidesNav from '~/components/BackendGuidesNav.astro';
 
-**Ready to add features like authentication, storage or data to your Astro project?** Follow one of our guides to integrate a backend service.
+**Ready to add features like authentication, monitoring, storage, or data to your Astro project?** Follow one of our guides to integrate a backend service.
 
 :::tip
 Find [community-maintained integrations](https://astro.build/integrations/) for adding popular features to your project in our integrations directory. 
@@ -29,3 +29,4 @@ You might want to consider a backend service if your project has complex server-
 - user-uploaded asset storage
 - API generation
 - realtime communication
+- application monitoring