Add Memento to productivity

Author: yaa110

categories/productivity.md

@@ -70,6 +70,7 @@ App Name                   | Describe                  | Major Language
 ###M
 App Name                   | Describe                  | Major Language             | Download 
 :------------------------: | :------------------------ | :------------------------: | :------------------------: 
+[Memento](https://github.com/yaa110/Memento) | A simple note taking app | Java | 
 [Minimal-Todo](https://github.com/avjinder/Minimal-Todo) | A fully Material ToDo app with minimal features, just enough to be useful. | Java |   
 
 ###N