$(document.head).append('<meta name="viewport" content="width=device-width, initial-scale=1.0" />');
$('head').append('<meta name="viewport" content="width=device-width, initial-scale=1.0" />');
... however due to a potential timing issue doing the above may not produce the result you desire because web-browser commonly only read the information within the head element when the HTML file is first loaded.
The best way to insure that that viewport meta data is used is to manually edit your story HTML file and added it to the head element, after you have created the story HTML file using the Publish to File option. You will need to redo this manual editing each time you create a new story HTML file.