title: How to do CKEditor 5 Image Uploading?
body: <pre><code>ClassicEditor
      .create( editorElement, {
          ckfinder: {
              uploadUrl: 'my_server_url'
          }
      } )
      .then( ... )
      .catch( ... );
  </code></pre>
  
  <p>What should be my server response? I am using Java in the backend.
  Whatever my response is, it throws a dialog box 'cannot upload file'.</p>