title: Create a luxon DateTime while keeping the original timezone offset
body: <p>If I have the following ISO date:</p>
  <pre><code>2021-07-05T13:20:00+06:00
  </code></pre>
  <p>If I call <code>DateTime.FromISO</code> it will convert it to machine local time, I then have to parse the string and set the zone manually.</p>
  <p>How do I create a luxon <code>DateTime</code> object with the offset of +06:00 as in the parsed string without the extra work?</p>
  <p>Please note, I know I can use <code>DateTime.fromISO(isoDate, { zone: 'utc' });</code> or any other zone, but do I have to really parse the iso string and get the zone manually to pass it to the <code>{zone: }</code> option?</p>