HtmlEditor is a drag & drop web page builder in only 286kb (based on boostrap) script in javascript Jquery and php built for developer . You can simply integrate this script in your web project and create custom html template with drag & drop.
Demo https://codecanyon.net/item/drag-drop-web-page-html-content-builder/13670257
Downloadhttps://www.filecad.com/mm1L/Drag-&-drop-web-page-html-content-builder.rar