code: function unescapeHTML(html, nestingDepth) {
    var div = document.createElement('div');
    for (var i = 0; i < nestingDepth; i++) {
      div.innerHTML = `<iframe srcdoc="${html}"></iframe>`;
      html = div.childNodes[0].attributes.srcdoc.value;
    }
    return html;
  }
docs: Take a string that represents valid HTML and unescape it so that it can be
  rendered.
  
  @param {string} html The HTML to unescape.
  @param {number} nestingDepth The number of times the HTML must be unescaped.
  @return {string} The unescaped HTML.