title: Drag & Drop Event in Quilljs
body: <p>I'm fairly new at Quill.</p>
  
  <p>I want to make a custom module or extended function that handles drag and drop event.
  I want to detect the dropped text, and if it's an image url, I want to insert 'img' tag instead of 'a' tag.</p>
  
  <p>Currently, Quill is adding 'a' tag for dropped url, but I cannot find related code.</p>