add huggingface model (#2624)

### What problem does this PR solve?

#2469

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

rag/llm/chat_model.py

@@ -1414,3 +1414,4 @@ class GoogleChat(Base):
                 yield ans + "\n**ERROR**: " + str(e)
 
             yield response._chunks[-1].usage_metadata.total_token_count
+