Update links

app.py

@@ -113,7 +113,7 @@ def get_description_text():
     
     This demo shows how to use the RetrieveUserProxyAgent and RetrieveAssistantAgent to build a chatbot.
 
-    #### [GitHub](https://github.com/microsoft/autogen) [Discord](https://discord.gg/pAbnFJrkgZ) [Blog](https://microsoft.github.io/autogen/blog/2023/10/18/RetrieveChat) [Paper](https://arxiv.org/abs/2308.08155)
+    #### [AutoGen](https://github.com/microsoft/autogen) [Discord](https://discord.gg/pAbnFJrkgZ) [Blog](https://microsoft.github.io/autogen/blog/2023/10/18/RetrieveChat) [Paper](https://arxiv.org/abs/2308.08155) [SourceCode](https://github.com/thinkall/autogen-demos)
     """