add support for csv file

chains/local_doc_qa.py

 from langchain.embeddings.huggingface import HuggingFaceEmbeddings
 from langchain.vectorstores import FAISS
-from langchain.document_loaders import UnstructuredFileLoader, TextLoader
+from langchain.document_loaders import UnstructuredFileLoader, TextLoader, CSVLoader
 from configs.model_config import *
 import datetime
 from textsplitter import ChineseTextSplitter
@@ -74,6 +74,9 @@ def load_file(filepath, sentence_size=SENTENCE_SIZE):
         loader = UnstructuredPaddleImageLoader(filepath, mode="elements")
         textsplitter = ChineseTextSplitter(pdf=False, sentence_size=sentence_size)
         docs = loader.load_and_split(text_splitter=textsplitter)
+    elif filepath.lower().endswith(".csv"):
+        loader = CSVLoader(filepath)
+        docs = loader.load()
     else:
         loader = UnstructuredFileLoader(filepath, mode="elements")
         textsplitter = ChineseTextSplitter(pdf=False, sentence_size=sentence_size)