WebEngine Widgets Simple Browser Example should include logic to handle/accept QWebEngineFullScreenRequest

The WebEngine Quick Nano Browser Example handles fullscreen requests. For example, when viewing a PDF document, the user can tap the "More Actions" menu (3 dots on the top-right) and select "Present" to enter fullscreen mode.

However, the WebEngine Widgets Simple Browser Example lacks this functionality.

Given that the functionality is non-trivial to implement, please add the ability to enter fullscreen mode (and exit fullscreen mode via the 'Esc' key) to the Widgets example, just like the Quick example.