add size details

README.md

@@ -10,6 +10,11 @@ dataset_info:
     dtype: string
   - name: openai
     sequence: float32
+  splits:
+  - name: train
+    num_bytes: 17782586772
+    num_examples: 1000000
+  download_size: 17782586772
   dataset_size: 1000000
 language:
 - en