code: function createCollapsible (header, content) {
    // XXX: duplicated
    return dom.create('div').class('qm-changelog-collapsible')
      .add(dom.create('div').class('qm-changelog-collapsible-heading')
        .add(dom.create('div').class('qm-changelog-collapsible-toggle')
          .add(dom.create('i').class('qm-changelog-chevron-icon')))
        .add(dom.create('div').class('qm-changelog-collapsible-head')
          .add(header)))
      .add(dom.create('div').class('qm-changelog-collapsible-content')
        .add(content))
  }
docs: /* Given header and content elements, this wraps them up into a collapsible