title: Pass variable to html template in nodemailer
body: <p>I want to send email with nodemailer using html template. In that template I need to inject some dynamically some variables and I really can't do that. My code:</p>
  
  <pre><code>var nodemailer = require('nodemailer');
  var smtpTransport = require('nodemailer-smtp-transport');
  
  smtpTransport = nodemailer.createTransport(smtpTransport({
      host: mailConfig.host,
      secure: mailConfig.secure,
      port: mailConfig.port,
      auth: {
          user: mailConfig.auth.user,
          pass: mailConfig.auth.pass
      }
  }));
  var mailOptions = {
      from: 'my@email.com',
      to : 'some@email.com',
      subject : 'test subject',
      html : { path: 'app/public/pages/emailWithPDF.html' }
  };
  smtpTransport.sendMail(mailOptions, function (error, response) {
      if (error) {
          console.log(error);
          callback(error);
      }
  });
  </code></pre>
  
  <p>Let's say I want in emailWithPDF.html something like this:</p>
  
  <pre><code>Hello {{username}}!
  </code></pre>
  
  <p>I've found some examples, where was smth like this:</p>
  
  <pre><code>...
  html: '&lt;p&gt;Hello {{username}}&lt;/p&gt;'
  ...
  </code></pre>
  
  <p>but I want it in separate html file. Is it possible?</p>