docs: add missing links to toc (#1163)

add missing links to toc

---------

Signed-off-by: Nan Wang <nan.wang@jina.ai>

docs/modules/chains/how_to_guides.rst

@@ -19,6 +19,7 @@ They are broken up into four categories:
    ./generic_how_to.rst
    ./combine_docs_how_to.rst
    ./utility_how_to.rst
+   ./async_chain.ipynb
 
 In addition to different types of chains, we also have the following how-to guides for working with chains in general:
 

docs/modules/llms/how_to_guides.rst

@@ -17,3 +17,5 @@ They are split into two categories:
 
    ./generic_how_to.rst
    ./integrations.rst
+   ./async_llm.ipynb
+   ./streaming_llm.ipynb