Update docs api references (#3315)

docs/reference.rst

@@ -7,8 +7,10 @@ Full documentation on all methods, classes, and APIs in LangChain.
 .. toctree::
    :maxdepth: 1
 
+   ./reference/models.rst
    ./reference/prompts.rst
-   LLMs<./reference/modules/llms>
-   ./reference/utils.rst
-   Chains<./reference/modules/chains>
-   Agents<./reference/modules/agents>
+   ./reference/indexes.rst
+   ./reference/modules/memory.rst
+   ./reference/modules/chains.rst
+   ./reference/agents.rst
+   ./reference/modules/utilities.rst