Create CITATION.cff (#672)

You may want to add doi/orcid

Followed this:
https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-citation-files

CITATION.cff

@@ -0,0 +1,9 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+- family-names: "Chase"
+  given-names: "Harrison"
+title: "LangChain"
+version: 0.0.66
+date-released: 2022-10-17
+url: "https://github.com/hwchase17/langchain"