readme: add language tags

Hi,

as part of the #Hacktoberfest [2023](https://github.com/huggingface/hub-docs/issues/986) this MR extends the dataset metadata and adds a language tag.

Happy merging!

README.md

@@ -18,6 +18,9 @@ configs:
   data_files:
   - split: train
     path: data/train-*
+language:
+- en
+- mr
 ---
 # Dataset Card for "t5-qe-2023-enmr-da-sys-test"