code: public WebhookMessageBuilder addFile(File file)
      {
          Checks.notNull(file, "File");
          return addFile(file.getName(), file);
      }
docs: Adds the provided file to the resulting message.
  <br>Shortcut for {@link #addFile(String, File)}.
  
  @param  file
  The file to add
  
  @throws IllegalArgumentException
  If the provided file is null, does not exist, or is not readable
  @throws IllegalStateException
  If the file limit has already been reached
  
  @return The current WebhookMessageBuilder for chaining convenience
  
  @see    #resetFiles()