chore: adding README information

Author: fguitton

README.md

@@ -1,3 +1,14 @@
 # c3po-app
 
-Mobile application for C3PO
+C3PO Exposure Notification Application.
+This application aims at providing a cross-platform proof-of-concept for a Contact Tracing enabled Exposure Notification.
+
+![Wireframe of C3PO](https://raw.githubusercontent.com/secretarium/c3po-app/master/resources/C3PO_wireframe_v5.svg)
+
+## Limitations
+
+There are multiple limitations related to the use of Bluetooth Low Energy for contact tracing component. See [`@secretarium/react-native-ble`](https://github.com/secretarium/c3po-react-native-ble#limitations) for more information.
+
+## License
+
+MIT