Add language tag

For better referencing :)

README.md

@@ -16,7 +16,10 @@ configs:
   data_files:
   - split: train
     path: data/train-*
+language:
+- fr
 ---
+
 # Dataset Card for "wikisource_fr"
 
 [More Information needed](https://github.com/huggingface/datasets/blob/main/CONTRIBUTING.md#how-to-contribute-to-the-dataset-cards)