Inject HTML into iframe

- widget HTML updated to remove unnecessary import of jQuery and widget common code, embed new embedHTML.js file, and add build expression for e2e mock data
- main.js updated to register/call params and apply logic for handling play/pause/stop
- Added `embedHTML.js`, module for encapsulating all code for configuring the iframe, retrieving the html value stored in settings, injecting the HTML into the iframe, and play/pause/stop behaviour
- Added mock-data for widget e2e and unit tests
- Updated gulp file to include mock-data in "html:e2e" task and added necessary test files for unit testing