code: public RequestFuture<?> send(File file, String fileName)
      {
          return send(new WebhookMessageBuilder().addFile(fileName, file).build());
      }
docs: Sends the provided {@link java.io.File File} to this webhook.
  <br>Use {@link WebhookMessage#files(String, Object, Object...)} to send up to 10 files!
  
  @param  file
  The file to send
  @param  fileName
  The name that should be used for this file
  
  @throws java.lang.IllegalArgumentException
  If the provided file is {@code null}, does not exist or is not readable
  @throws java.util.concurrent.RejectedExecutionException
  If this client was closed
  
  @return {@link net.dv8tion.jda.core.requests.RequestFuture RequestFuture} representing the execution task,
  this will be completed once the message was sent.