code: function writeSubTable12(writer, segments) {
  
              writer.writeUint16(12); // format
              writer.writeUint16(0); // reserved
              writer.writeUint32(16 + segments.length * 12); // length
              writer.writeUint32(0); // language
              writer.writeUint32(segments.length); // nGroups
  
              segments.forEach(function (segment) {
                  writer.writeUint32(segment.start);
                  writer.writeUint32(segment.end);
                  writer.writeUint32(segment.startId);
              });
  
              return writer;
          }
docs: 创建`子表12`
  
  @param {Writer} writer 写对象
  @param {Array} segments 分块编码列表
  @return {Writer}