code: private void _hashname() throws
        IOException,
        CssException
    {
      if (debug)
      {
        checkState(reader.curChar == '#');
        checkState(NMCHAR.matches((char) reader.peek()) || isNextEscape());
      }
      builder.type = Type.HASHNAME;
      builder.append('#');
      append(NMCHAR);
    }
docs: HASHNAME "#"{name} name {nmchar}+ [_a-z0-9-]|{nonascii}|{escape}
  
  @throws CssException