title: Missing method in JavaScript API for Excel: copy a sheet
body: <p>Since there is no way to cancel the changes made by an add-in, we need to provide users with backup options. </p>
  
  <p>The current version of JavaScript API for Excel doesn't have a method for copying a sheet with its data and formatting.</p>
  
  <p>Does anyone know of any workarounds or plans for adding such method?</p>