Pre-study: Implement Push Notifications

[RoiJS]

Do some research on how to implement push notification on mobile android application

[RoiJS]

Done doing some research and a little bit of coding.

@nativescript/firebase - plugin to be used on nativescript app
FirebaseAdmin SDK - plugin to use on server-side

There is a little bit of problem on using push notification on android because at this moment, the nativescript plugin does not support "click_action" this means that there is no way to customize the click event on the push notification, eg. opening specific page after tapping on the notification.