community[minor]: Implement lazy_load() for FacebookChatLoader (langc…

…hain-ai#18669)

Integration test:
`tests/integration_tests/document_loaders/test_facebook_chat.py`

libs/community/langchain_community/document_loaders/facebook_chat.py

@@ -1,7 +1,7 @@
 import datetime
 import json
 from pathlib import Path
-from typing import List
+from typing import Iterator
 
 from langchain_core.documents import Document
 
@@ -29,8 +29,7 @@ def __init__(self, path: str):
         """Initialize with a path."""
         self.file_path = path
 
-    def load(self) -> List[Document]:
-        """Load documents."""
+    def lazy_load(self) -> Iterator[Document]:
         p = Path(self.file_path)
 
         with open(p, encoding="utf8") as f:
@@ -43,4 +42,4 @@ def load(self) -> List[Document]:
         )
         metadata = {"source": str(p)}
 
-        return [Document(page_content=text, metadata=metadata)]
+        yield Document(page_content=text, metadata=metadata)