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/google/roberta2roberta_L-24_gigaword/README.md

README.md

@@ -0,0 +1,39 @@
+---
+language: en
+license: apache-2.0
+datasets:
+- gigaword
+tags:
+- summarization
+---
+
+# Roberta2Roberta_L-24_gigaword EncoderDecoder model
+
+The model was introduced in 
+[this paper](https://arxiv.org/abs/1907.12461) by Sascha Rothe, Shashi Narayan, Aliaksei Severyn and first released in [this repository](https://tfhub.dev/google/bertseq2seq/roberta24_gigaword/1). 
+
+The model is an encoder-decoder model that was initialized on the `roberta-large` checkpoints for both the encoder 
+and decoder and fine-tuned on headline generation using the Gigaword dataset, which is linked above.
+
+Disclaimer: The model card has been written by the Hugging Face team.
+
+## How to use
+
+You can use this model for extreme summarization, *e.g.*
+
+```python
+from transformers import AutoTokenizer, AutoModelForSeq2SeqLM
+
+tokenizer = AutoTokenizer.from_pretrained("google/roberta2roberta_L-24_gigaword")
+model = AutoModelForSeq2SeqLM.from_pretrained("google/roberta2roberta_L-24_gigaword")
+
+article = """australian shares closed down #.# percent monday
+following a weak lead from the united states and
+lower commodity prices , dealers said ."""
+
+input_ids = tokenizer(article, return_tensors="pt").input_ids
+output_ids = model.generate(input_ids)[0]
+print(tokenizer.decode(output_ids, skip_special_tokens=True))
+# should output
+# australian shares close down #.# percent.
+```