Add configurable native glass window backgrounds

README.md

@@ -62,7 +62,11 @@ like an explanation, expand the small **Why this result?** detail.
 
 Light and dark themes follow your system preference. Keyboard navigation,
 short transitions and reduced-motion support keep the interface familiar
-and comfortable.
+and comfortable. In **Settings → Appearance**, choose a solid, glass or
+frosted-glass window background and adjust its tint. Reading surfaces stay
+clear. Native glass currently requires **Windows 11 22H2 or later**. macOS,
+Linux, unsupported Windows versions and high-contrast mode currently use a
+solid background; your appearance preference is retained.
 
 ![searchi finding and previewing a mountain lake photograph](docs/screenshots/media-search.png)