Migrate model card from transformers-repo

Read announcement at https://discuss.huggingface.co/t/announcement-all-model-cards-will-be-migrated-to-hf-co-model-repos/2755
Original file history: https://github.com/huggingface/transformers/commits/master/model_cards/akhooli/mbart-large-cc25-ar-en/README.md

README.md

@@ -0,0 +1,15 @@
+---
+tags:
+- translation
+
+language:
+- ar
+- en
+
+license: mit
+---
+### mbart-large-ar-en
+This is mbart-large-cc25, finetuned on a subset of the OPUS corpus for ar_en.   
+Usage: see [example notebook](https://colab.research.google.com/drive/1I6RFOWMaTpPBX7saJYjnSTddW0TD6H1t?usp=sharing)  
+Note: model has limited training set, not fully trained (do not use for production).   
+Other models by me: [Abed Khooli](https://huggingface.co/akhooli)