Tawk CallBacks

[randomlee101]

Implementation of JavaScript Channels to listen to events from the WebView housing the Tawk web widget.

New Files:

tawk_events_js.dart

New Parameters:

To affix a callback for consumption from the parent widget

ValueChanged 

To listen to all the javascript channels as a set

javascriptChannels

This receives messages peculiar to the various channels and we can further process the message in the case of a JSON data using:

jsonDecode(e.message)

N.B: Only a few of the events have been accounted for as of this pull request and verification via the example library will be appreciated to proceed with the remaining events.

In the process of testing these updates, kindly provide sample responses to aid developing models for each callbacks so as to create typed ValueChanged callbacks