Fix: Vue3 global properties not available in slot

[MrSnoozles]

This PR makes global properties available in the slot. Global properties are not recommended to use, but are part of Vue3 to enable migration from Vue2 projects.

Current behaviour

The following code will throw an error, because $L is not defined on the context.

// app.ts

const app = createApp({});
app.config.globalProperties.$L = localize;

// MyList.vue

<CollectionView :items="items">
   <template #default="{ item }">
       <Label :text="$L('Hello world')" />
   </template>
</CollectionView>