refactor(WebRTC): add NotificationCtrl on the layout

Notes:
This controller will listen on the notify event, specifically when someone is calling.

Take a look at the source here:
https://github.com/mykabam/kabam-plugin-webrtc/blob/cc234b41465273abea9c874f37c1de9c727a3541/assets/public/webrtc/call/controllers/notification.js

This controller exists since kabam-plugin-webrtc v0.3.11
Merge branch 'notification'