Xamarin.Forms.macOS: AnimationView not visible

## 🐛 Bug Report

Lottie is visible in Xamarin.Forms.macOS.

Because there is support for Xamarin.macOS I am not sure if its a bug or there is no implementation.

### Expected behavior
`AnimationView` is visible

### Reproduction steps
- Create new Xamarin.Forms.macOS app
- Add `AnimationView` to your XAML page

### Configuration

**Version:** 2.5.10

**Platform:**
- [ ] :iphone: iOS
- [ ] :robot: Android
- [ ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [x] :monkey: Xamarin.Forms

Start by reproducing the issue in a new Xamarin.Forms.macOS app using the reported 2.5.10 configuration and an AnimationView in XAML. Then locate the Xamarin.Forms.macOS AnimationView implementation and compare it with the supported Xamarin.macOS behavior. Done means AnimationView is visible in the reported reproduction.

Written by the indexing model from the issue text.