Add evaluation results on the default config and test split of gigaword

Beep boop, I am a bot from Hugging Face's automatic model evaluator 👋!\
Your model has been evaluated on the default config and test split of the [gigaword](https://huggingface.co/datasets/gigaword) dataset by

@geiright

, using the predictions stored [here](https://huggingface.co/datasets/autoevaluate/autoeval-eval-gigaword-default-2df74a-2350473902).\
Accept this pull request to see the results displayed on the [Hub leaderboard](https://huggingface.co/spaces/autoevaluate/leaderboards?dataset=gigaword).\
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README.md

@@ -43,6 +43,39 @@ model-index:
       type: gen_len
       value: 78.5866
       verified: true
+  - task:
+      type: summarization
+      name: Summarization
+    dataset:
+      name: gigaword
+      type: gigaword
+      config: default
+      split: test
+    metrics:
+    - name: ROUGE-1
+      type: rouge
+      value: 16.4548
+      verified: true
+    - name: ROUGE-2
+      type: rouge
+      value: 5.2209
+      verified: true
+    - name: ROUGE-L
+      type: rouge
+      value: 14.0704
+      verified: true
+    - name: ROUGE-LSUM
+      type: rouge
+      value: 14.7993
+      verified: true
+    - name: loss
+      type: loss
+      value: 4.663515567779541
+      verified: true
+    - name: gen_len
+      type: gen_len
+      value: 63.7811
+      verified: true
 ---
 # BART (large-sized model), fine-tuned on CNN Daily Mail