Dark Mode Support

Hi. Dark mode usage is growing on all platforms. One day I opened my own email in the night when dark mode was switched on automatically on my smartphone and I was shocked how it looked. At the same time when I opened it in webmail client the email was also dark but has another look. Please let us switch to dark mode in preview and add some special styles for dark mode as described here https://www.litmus.com/blog/the-ultimate-guide-to-dark-mode-for-email-marketers/ so we can adjust how our email looks when dark mode is on.