feat: enable shadows by default for undecorated window on Windows (#732)

.changes/windows-undecorated-shadow.md

@@ -0,0 +1,5 @@
+---
+"tao": "minor"
+---
+
+Enable shadows by default for undecorated window on Windows.

src/platform_impl/windows/mod.rs

@@ -63,7 +63,7 @@ impl Default for PlatformSpecificWindowBuilderAttributes {
       drag_and_drop: true,
       preferred_theme: None,
       skip_taskbar: false,
-      decoration_shadow: false,
+      decoration_shadow: true,
     }
   }
 }