Update README.md

Adds a link to the Chechen extension

README.md

@@ -315,6 +315,7 @@ If you use any of the data released in our work, please cite the following paper
 
 ## Extensions of this benchmark
 - https://huggingface.co/datasets/ZurichNLP/wmt24pp-rm (German → 6 varieties of Romansh)
+- https://huggingface.co/datasets/NM-development/wmt24pp-ce (English → Chechen) from Vladislav Grigorian and Abu-Viskhan Umishov
 
 ## Helpful Python Constants