next(loop = false) {
    const maxIndex = this.length - 1;
    let index = this.index + 1;

    if (index > maxIndex) {
      index = loop ? 0 : maxIndex;
    }

    this.view(index);
    return this;
  }
View the next image
@param {boolean} [loop=false] - Indicate if view the first one
when it is the last one at present.
@returns {Viewer} this