added prompt library to main index

Author: Tracey Carter

index.rst

@@ -286,6 +286,11 @@ To keep up to date with changes in the products, see the Splunk Observability Cl
 .. toctree::
    :maxdepth:   3   
 
+   AI Assistant in Observability Cloud <get-started/o11y-ai-promptlibrary>
+
+.. toctree::
+   :maxdepth:   3  
+
    Architecture <get-started/o11y-architecture>
 
 .. toctree::