feat: support switch component

AppWindow.qml

@@ -15,6 +15,8 @@ ApplicationWindow {
         brightText: Theme.muted
         text: Theme.foreground
         button: Theme.accent
+        midlight: Theme.card
+        light: Theme.secondaryText
     }
 
     title: qsTr("Flowy")

gallery/Main.qml

@@ -47,5 +47,7 @@ AppWindow {
           }
         }
       }
+
+      Switch {}
     }
 }