add 3 property types in metadata for notiondb loader (#8509)

### Description: 
NotionDB supports a number of common property types. I have found three
common types that are not included in notiondb loader. When programs
loaded them with notiondb, which will cause some metadata information
not to be passed to langchain. Therefore, I added three common types:
- date
- created_time
- last_edit_time.

### Issue: 
no
### Dependencies: 
No dependencies added :)
### Tag maintainer: 
@rlancemartin, @eyurtsev
### Twitter handle: 
@BJTUTC

libs/langchain/langchain/document_loaders/notiondb.py

@@ -120,6 +120,12 @@ class NotionDBLoader(BaseLoader):
                     if prop_data["people"]
                     else []
                 )
+            elif prop_type == "date":
+                value = prop_data["date"]
+            elif prop_type == "created_time":
+                value = prop_data["created_time"]
+            elif prop_type == "last_edited_time":
+                value = prop_data["last_edited_time"]
             else:
                 value = None