code: public Jar addEntries(Path path, ZipInputStream zip) throws IOException {
          return addEntries(path, zip, null);
      }
docs: Adds the contents of the zip/JAR contained in the given byte array to this JAR.
  
  @param path the path within the JAR where the root of the zip will be placed, or {@code null} for the JAR's root
  @param zip  the contents of the zip/JAR file
  @return {@code this}