code: public Section addSection(String title, File... files) throws IOException {
          return add(null, title, files);
      }
docs: Adds a custom section from one or more files, that isn't related to any element in the model.
  
  @param title             the section title
  @param files             one or more File objects that point to the documentation content
  @return                  a documentation {@link Section}
  @throws IOException      if there is an error reading the files