setTitle(text) {
    this.domElement.title = text;
    ifChild(this.domElement, this.options.cssprefix, 'title', (title)=> {
      if (!text) {
        title.style.display = 'none';
      } else {
        title.innerText = text;
        title.style.display = 'initial';
      }
    });

    return this;
  }
Set the title of the button
@param {string} text
@return {EnterVRButton}