meta: integrate wallpaper, FileBrowser, StateLayer

- A lot of this is implements patterns implemented by soramannew's
  caelestia-shell

Widgets/StyledRect.qml

@@ -0,0 +1,37 @@
+import QtQuick
+import qs.Common
+
+Rectangle {
+    id: root
+
+    color: "transparent"
+    radius: Appearance.rounding.normal
+
+    Behavior on color {
+        ColorAnimation {
+            duration: Appearance.anim.durations.normal
+            easing.type: Easing.BezierSpline
+            easing.bezierCurve: Appearance.anim.curves.standard
+        }
+
+    }
+
+    Behavior on radius {
+        NumberAnimation {
+            duration: Appearance.anim.durations.normal
+            easing.type: Easing.BezierSpline
+            easing.bezierCurve: Appearance.anim.curves.standard
+        }
+
+    }
+
+    Behavior on opacity {
+        NumberAnimation {
+            duration: Appearance.anim.durations.normal
+            easing.type: Easing.BezierSpline
+            easing.bezierCurve: Appearance.anim.curves.standard
+        }
+
+    }
+
+}