preview publish option for pages similar to quick publish on sites.html

I am building one preview functionality in AEM to publish the content to preview server first to review the pages before publishing to actual publish instance. To meet the requirement, I have overlayed the sites node from libs to apps (wcm/core/content/sites) and added new preview publish node under jcr:content/actions/selection which is now visible in sites.html after selecting a page. I want to add a custom java script and pop up dialog to add a custom action on it. Can someone suggest the steps to attach custom actions on the new preview publish button?