Update ref.txt

ref.txt

@@ -1 +1,2 @@
-1. https://stackoverflow.com/questions/78028402/modulenotfounderror-for-llama-index-vector-stores-in-python-project
+1. https://stackoverflow.com/questions/78028402/modulenotfounderror-for-llama-index-vector-stores-in-python-project
+2. https://github.com/NirDiamant/RAG_Techniques/blob/main/all_rag_techniques/simple_csv_rag_with_llamaindex.ipynb