Add api cross ref linking (#8275)

Example of how it would show up in our python docs:


![image](https://github.com/langchain-ai/langchain/assets/13333726/0f0a88cc-ba4a-4778-bc47-118c66807f15)


Examples added to the reference docs:

https://api.python.langchain.com/en/wfh-api_crosslink/vectorstores/langchain.vectorstores.chroma.Chroma.html#langchain.vectorstores.chroma.Chroma


![image](https://github.com/langchain-ai/langchain/assets/13333726/dcd150de-cb56-4d42-b49a-a76a002a5a52)

docs/api_reference/create_api_rst.py

@@ -78,6 +78,7 @@ Functions
 
 .. autosummary::
     :toctree: {module}
+    :template: function.rst
 
     {fstring}