Adding customer stories to TOC

Author: JasonWHowell

articles/mysql/TOC.yml

@@ -135,3 +135,5 @@
     href: https://azure.microsoft.com/regions/services/
   - name: Support options
     href: https://azure.microsoft.com/support/options/
+  - name: Customer stories
+    href: https://customers.microsoft.com/search?sq="Azure%20Database%20for%20MySQL%20"

articles/postgresql/TOC.yml

@@ -123,3 +123,5 @@
     href: https://azure.microsoft.com/regions/services/
   - name: Support options
     href: https://azure.microsoft.com/support/options/
+  - name: Customer stories
+    href: https://customers.microsoft.com/search?sq="Azure%20Database%20for%20PostgreSQL%20"