dark mode improvements

src/scss/layout/_dark.scss

@@ -42,6 +42,7 @@ body:not(.theme-dark) .hide-theme-light {
       --#{$prefix}#{$color}-lt-rgb: #{to-rgb(theme-color-lighter($value, $dark))};
     }
 
+    color-scheme: dark;
     color: $dark-mode-text;
     background-color: $dark-mode-darken;
   }