QmlDesigner.ItemLibrary: Adding support for StackLayout

The StackLayout is working and it makes sense to add it to the
item library.

Change-Id: I732398a25091f2a33f38c42f5bf1c55ef9dac237
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/qmldesigner/componentsplugin/components.metainfo

@@ -342,6 +342,22 @@ MetaInfo {
         }
     }
 
+Type {
+    name: "QtQuick.Layouts.StackLayout"
+    icon: ":/componentsplugin/images/stack-layouts-icon-16px.png"
+
+    ItemLibraryEntry {
+        name: "StackLayout"
+        category: "Qt Quick - Layouts"
+        libraryIcon: ":/componentsplugin/images/stack-layouts-icon.png"
+        version: "1.3"
+        requiredImport: "QtQuick.Layouts"
+
+        Property { name: "width"; type: "int"; value: 100; }
+        Property { name: "height"; type: "int"; value: 100; }
+    }
+}
+
     Type {
         name: "QtQuick.Controls.TabView"
         icon: ":/componentsplugin/images/window16.png"

src/plugins/qmldesigner/componentsplugin/componentsplugin.qrc

@@ -43,6 +43,8 @@
         <file>images/row-layouts-icon-16px.png</file>
         <file>images/splitview-layouts-icon.png</file>
         <file>images/splitview-layouts-icon-16px.png</file>
+        <file>images/stack-layouts-icon.png</file>
+        <file>images/stack-layouts-icon-16px.png</file>
     </qresource>
     <qresource prefix="/propertyEditorQmlSources/QtQuick">
         <file>Controls/ButtonSpecifics.qml</file>