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

@@ -60,10 +60,10 @@ dataset_info:
       dtype:
         class_label:
           names:
-            0: StrongNegative
-            1: Negative
-            2: Positive
-            3: StrongPositive
+            '0': StrongNegative
+            '1': Negative
+            '2': Positive
+            '3': StrongPositive
     - name: opinion_expression_target
       sequence: string
   splits:
@@ -108,10 +108,10 @@ dataset_info:
       dtype:
         class_label:
           names:
-            0: StrongNegative
-            1: Negative
-            2: Positive
-            3: StrongPositive
+            '0': StrongNegative
+            '1': Negative
+            '2': Positive
+            '3': StrongPositive
     - name: opinion_expression_target
       sequence: string
   splits: