Feature request: pick up on INotifyCollectionChanged changes to ItemsSource

[mfeingol]

That way the user can use an ObservableCollection and doesn't have to replace the existing collection. Much more aligned with how other ItemsSource properties work out there.

E.g. like this:

    /// <summary>
    /// Maps the <see cref="IAutoSuggestBox.ItemsSource"/> property to the native AutoSuggestBox control.
    /// </summary>
    /// <param name="handler">View handler</param>
    /// <param name="autoSuggestBox">IAutoSuggestBox instance</param>
    public static void MapItemsSource(AutoSuggestBoxHandler handler, IAutoSuggestBox autoSuggestBox)
    {
#if WINDOWS
    handler.PlatformView.ItemsSource = autoSuggestBox?.ItemsSource;
#elif __ANDROID__ || __IOS__
        // Unhook previous subscription
        if (handler.ItemsSourceSubscription is INotifyCollectionChanged oldNcc)
            oldNcc.CollectionChanged -= handler.OnItemsSourceCollectionChanged;

        // Apply initial items
        handler.PlatformView.SetItems(
            autoSuggestBox?.ItemsSource?.OfType<object>(),
            o => FormatType(o, autoSuggestBox?.DisplayMemberPath),
            o => FormatType(o, autoSuggestBox?.TextMemberPath)
        );

        // Hook new subscription
        if (autoSuggestBox?.ItemsSource is INotifyCollectionChanged ncc)
        {
            handler.ItemsSourceSubscription = ncc;
            ncc.CollectionChanged += handler.OnItemsSourceCollectionChanged;
        }
        else
        {
            handler.ItemsSourceSubscription = null;
        }
#endif
    }

#if __ANDROID__ || __IOS__
    INotifyCollectionChanged? ItemsSourceSubscription { get; set; }

    void OnItemsSourceCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
    {
        if (VirtualView is not IAutoSuggestBox autoSuggestBox)
            return;

        PlatformView.SetItems(
            autoSuggestBox.ItemsSource?.OfType<object>(),
            o => FormatType(o, autoSuggestBox.DisplayMemberPath),
            o => FormatType(o, autoSuggestBox.TextMemberPath)
        );
    }
#endif