Add link to paper, task categories

This PR adds a link to the paper and task categories to the dataset card.

README.md

@@ -1,10 +1,13 @@
 ---
 license: mit
 configs:
-  - config_name: Difficulty Score
-    data_files: Qwen2.5-Math-7B--deepscaler--difficulty.csv
-  - config_name: Response
-    data_files: Qwen2.5-Math-7B--deepscaler.csv
+- config_name: Difficulty Score
+  data_files: Qwen2.5-Math-7B--deepscaler--difficulty.csv
+- config_name: Response
+  data_files: Qwen2.5-Math-7B--deepscaler.csv
+task_categories:
+- reinforcement-learning
+- reasoning
 ---
 
 # Difficulty Estimation on DeepScaleR