fix: add accent-color/color-scheme (#2088)

src/scss/themes/_base.scss

@@ -133,4 +133,7 @@
   --blurhash-sensitive-text-color: #{lighten($deemphasized-color, 40%)};
 
   --focus-bg: #{rgba(0, 0, 0, 0.1)};
+
+  accent-color: #{$main-theme-color};
+  color-scheme: light dark;
 }

src/scss/themes/_dark.scss

@@ -52,4 +52,6 @@
   --blurhash-sensitive-text-color: #{lighten($deemphasized-color, 15%)};
 
   --focus-bg: #{rgba(255, 255, 255, 0.1)};
+
+  color-scheme: dark light;
 }