code: function CustomHtml(options) {
          this.button = document.createElement('button');
          this.button.className = 'medium-editor-action';
          if (this.button.innerText) {
              this.button.innerText = options.buttonText || "</>";
          } else {
              this.button.textContent = options.buttonText || "</>";
          }
          this.button.onclick = this.onClick.bind(this);
          this.options = options;
      }
docs: CustomHtml
  Creates a new instance of CustomHtml extension.
  
  Licensed under the MIT license.
  Copyright (c) 2014 jillix
  
  @name CustomHtml
  @function
  @param {Object} options An object containing the extension configuration. The
  following fields should be provided:
  - buttonText: the text of the button (default: `</>`)
  - htmlToInsert: the HTML code that should be inserted