Replace YAML keys from int to str

Replace YAML metadata integer keys with strings, as the Hub does not support integers.
See: https://github.com/huggingface/datasets/issues/5275

README.md

@@ -40,8 +40,8 @@ dataset_info:
       dtype:
         class_label:
           names:
-            0: USER
-            1: SYSTEM
+            '0': USER
+            '1': SYSTEM
     - name: utterance
       dtype: string
     - name: frames
@@ -124,8 +124,8 @@ dataset_info:
       dtype:
         class_label:
           names:
-            0: USER
-            1: SYSTEM
+            '0': USER
+            '1': SYSTEM
     - name: utterance
       dtype: string
     - name: frames