Allow PackageList to be used as a model from QML

QML is leading here and holding the pointers for creation and destruction.

Contributes to issue CURA-8556.

plugins/Marketplace/resources/qml/Plugins.qml

@@ -2,8 +2,18 @@
 // Cura is released under the terms of the LGPLv3 or higher.
 
 import QtQuick 2.15
+import QtQuick.Controls 2.15
+import Cura 1.7 as Cura
 
-Rectangle
+Item
 {
-    color: "pink" //TODO
+    Repeater
+    {
+        model: Cura.PackageList{}
+
+        Label
+        {
+            text: "Test"  //TODO: Create a card for each package.
+        }
+    }
 }