Harrison/wiki update (#622)

Co-authored-by: Rubens Mau <[email protected]>

Author: hwchase17

langchain/docstore/wikipedia.py

@@ -30,7 +30,10 @@ def search(self, search: str) -> Union[str, Document]:
 
         try:
             page_content = wikipedia.page(search).content
-            result: Union[str, Document] = Document(page_content=page_content)
+            url = wikipedia.page(search).url
+            result: Union[str, Document] = Document(
+                page_content=page_content, metadata={"page": url}
+            )
         except wikipedia.PageError:
             result = f"Could not find [{search}]. Similar: {wikipedia.search(search)}"
         except wikipedia.DisambiguationError: