Add info for GeLU layer in readme (#484)

* update Gelu info in readme

Author: AakashKumarNain

tensorflow_addons/layers/README.md

@@ -3,6 +3,7 @@
 ## Maintainers
 | Submodule  |  Maintainers  | Contact Info   |
 |:---------- |:----------- |:------------- |
+| gelu       | @AakashKumarNain | aakashnain@outlook.com |  
 | maxout |  |  |
 | normalizations | @smokrow | moritz.kroeger@tu-dortmund.de |
 | opticalflow |  |  |
@@ -13,6 +14,7 @@
 ## Components
 | Submodule  | Layer |  Reference  |
 |:---------- |:----------- |:------------- |
+| gelu   | GeLU   | https://arxiv.org/abs/1606.08415 | 
 | maxout | Maxout | https://arxiv.org/abs/1302.4389    |
 | normalizations | GroupNormalization | https://arxiv.org/abs/1803.08494 |
 | normalizations | InstanceNormalization | https://arxiv.org/abs/1607.08022 |