Change theme based on monitor size

[DaveDavenport]

Since 1.6.0 you can change your theme based on monitor size or ratio.
For example if you want on your full-hd monitor to go fullscreen, but not on the 4k monitor, you can add something like:

@media (max-width: 1921 ) {
  window {
    fullscreen: true;
  }
}