Upload links to reference data 'laws service content'

Upload 'laws service content' corresponding to each label description of reference material and link.

README.md

@@ -58,6 +58,10 @@ An example of 'train' looks as follows.
    'laws_service_id': 7
 }
 ```
+ Other References
+You can refer to each label's 'laws service content' [here](https://storage.googleapis.com/klaid/ljp/dataset/ljp_laws_service_content.json).
+'Laws service content' is the statute([source](https://www.law.go.kr/)) corresponding to each label.
+
 ### Data Fields
 #### ljp
 + "fact": a `string` feature