Adding eval metadata for AG News (#4329)

Adding eval metadata for AG News

Commit from https://github.com/huggingface/datasets/commit/6668b6e12ed93abe2a7701f6a372fdda4ba80dcc

README.md

@@ -19,6 +19,55 @@ task_ids:
 - topic-classification
 paperswithcode_id: ag-news
 pretty_name: AG’s News Corpus
+train-eval-index:
+- config: default
+  task: text-classification
+  task_id: multi_class_classification
+  splits:
+    train_split: train
+    eval_split: test
+  col_mapping:
+    text: text
+    label: target
+  metrics:
+    - type: accuracy
+      name: Accuracy
+    - type: f1
+      name: F1 macro
+      args:
+        average: macro
+    - type: f1
+      name: F1 micro
+      args:
+        average: micro  
+    - type: f1
+      name: F1 weighted
+      args:
+        average: weighted
+    - type: precision
+      name: Precision macro
+      args:
+        average: macro  
+    - type: precision
+      name: Precision micro
+      args:
+        average: micro  
+    - type: precision
+      name: Precision weighted
+      args:
+        average: weighted  
+    - type: recall
+      name: Recall macro
+      args:
+        average: macro  
+    - type: recall
+      name: Recall micro
+      args:
+        average: micro  
+    - type: recall
+      name: Recall weighted
+      args:
+        average: weighted
 ---
 
 # Dataset Card for "ag_news"