chore: Reference Raygun docs in toc

doc/articles/toc.yml

@@ -274,6 +274,8 @@
           href: features/upri-trimming.md
         - name: Working with XAML Trimming
           href: features/resources-trimming.md
+        - name: Error Monitoring & Crash Reporting with Raygun
+          href: xref:Monitoring.Raygun
 
     - name: Contributing
       items: