Added license info (#4)

- Added license info (5f8adeaa7c9776886ad8620c2848fc11a156828a)


Co-authored-by: Florent Gbelidji <florentgbelidji@users.noreply.huggingface.co>

README.md

@@ -1,5 +1,6 @@
 ---
 language: en
+license: apache-2.0
 ---
 
 # longformer-base-4096
@@ -24,4 +25,4 @@ If you use `Longformer` in your research, please cite [Longformer: The Long-Docu
 ```
 
 `Longformer` is an open-source project developed by [the Allen Institute for Artificial Intelligence (AI2)](http://www.allenai.org).
-AI2 is a non-profit institute with the mission to contribute to humanity through high-impact AI research and engineering.
+AI2 is a non-profit institute with the mission to contribute to humanity through high-impact AI research and engineering.