function sendEmailNotificationTemplate(content, emailAddress) {
  let template = HtmlService.createTemplateFromFile('email');
  template.content = content;
  let msg = template.evaluate();  
  MailApp.sendEmail(emailAddress,'New comments or replies on YouTube',msg.getContent(),{htmlBody:msg.getContent()});
}
Assembles notification email with table of video details. 
(h/t https://stackoverflow.com/questions/37863392/making-table-in-google-apps-script-from-array)