There are several steps in the process:
1. add an Event Listeners that listens for a CNTRL-ENTER key combination.
2. Have that listener launch a function that toggles the full screen mode
3. Make sure your HTML embed code allows for Full Screen mode.
Note: You can't test this feature in the development enviornment. You have to publish, upload to the server, and test it that way.
Here's a few links for a more thurough breakdown:
For listening for key presses:
For a list of keycodes:
Note that there is no key code for CNTRL-ENTER. You'll have to be creative with it. I would suggest coming up with a Boolean variable for CNTRL being down, and one for ENTER being down. If both variables return true, then launch the fullscreen function.
For writing the fullscreen function: