widgets: add wrapper components and managers

src/widgets/WrapperItem.qml

@@ -0,0 +1,44 @@
+import QtQuick
+import Quickshell.Widgets
+
+///! Item that handles sizes and positioning for a single visual child.
+/// This component is useful when you need to wrap a single component in
+/// an item, or give a single component a margin. See [QtQuick.Layouts]
+/// for positioning multiple items.
+///
+/// > [!NOTE] WrapperItem is a @@MarginWrapperManager based component.
+/// > You should read its documentation as well.
+///
+/// ### Example: Adding a margin to an item
+/// The snippet below adds a 10px margin to all sides of the @@QtQuick.Text item.
+///
+/// ```qml
+/// WrapperItem {
+///   margin: 10
+///
+///   @@QtQuick.Text { text: "Hello!" }
+/// }
+/// ```
+///
+/// > [!NOTE] The child item can be specified by writing it inline in the wrapper,
+/// > as in the example above, or by using the @@child property. See
+/// > @@WrapperManager.child for details.
+///
+/// > [!WARNING] You should not set @@Item.x, @@Item.y, @@Item.width,
+/// > @@Item.height or @@Item.anchors on the child item, as they are used
+/// > by WrapperItem to position it. Instead set @@Item.implicitWidth and
+/// > @@Item.implicitHeight.
+///
+/// [QtQuick.Layouts]: https://doc.qt.io/qt-6/qtquicklayouts-index.html
+Item {
+	/// The minimum margin between the child item and the WrapperItem's edges.
+	/// Defaults to 0.
+	property /*real*/alias margin: manager.margin
+	/// If the child item should be resized larger than its implicit size if
+	/// the WrapperItem is resized larger than its implicit size. Defaults to false.
+	property /*bool*/alias resizeChild: manager.resizeChild
+	/// See @@WrapperManager.child for details.
+	property /*Item*/alias child: manager.child
+
+	MarginWrapperManager { id: manager }
+}