Create bigbench.yml

lm_eval/tasks/siqa/bigbench.yml

+task: social_iqa
+dataset_path: social_i_qa
+dataset_name: null
+output_type: multiple_choice
+training_split: train
+validation_split: validation
+doc_to_text: "Q: {{context}} {{question}}\nA:"
+target_delimiter: " "
+doc_to_choice: ["{{answerA}}", "{{answerB}}", "{{answerC}}"]
+doc_to_target: "{{label}}"
+metric_list:
+  - metric: acc
+    aggregation: mean
+    higher_is_better: true