Add evaluation results on xsum dataset

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

@ArjunPrSarkhel

, using the predictions stored [here](https://huggingface.co./datasets/autoevaluate/autoeval-staging-eval-project-xsum-7db0303b-10095338).\
Accept this pull request to see the results displayed on the [Hub leaderboard](https://huggingface.co./spaces/autoevaluate/leaderboards?dataset=xsum).\
Evaluate your model on more datasets [here](https://huggingface.co./spaces/autoevaluate/model-evaluator?dataset=xsum).

README.md

@@ -49,6 +49,39 @@ model-index:
       type: gen_len
       value: 59.6032
       verified: true
+  - task:
+      type: summarization
+      name: Summarization
+    dataset:
+      name: xsum
+      type: xsum
+      config: default
+      split: test
+    metrics:
+    - name: ROUGE-1
+      type: rouge
+      value: 21.1644
+      verified: true
+    - name: ROUGE-2
+      type: rouge
+      value: 4.0659
+      verified: true
+    - name: ROUGE-L
+      type: rouge
+      value: 13.9414
+      verified: true
+    - name: ROUGE-LSUM
+      type: rouge
+      value: 17.0718
+      verified: true
+    - name: loss
+      type: loss
+      value: 3.002755880355835
+      verified: true
+    - name: gen_len
+      type: gen_len
+      value: 71.2969
+      verified: true
 ---
 
 ## `distilbart-cnn-12-6-samsum`