SkiaUI

Using Skia, Yoga to build a simple Flexbox-UI framework for iOS.

steps：

1. Compile skia https://skia.org/docs/user/build/
2. Using Skia Metal context.
3. Two threads: ui-thread & render-thread.
4. Only support FlexboxLayout. Measure/Layout/Draw are triggered by Vsync.
5. TouchEvents: dispatchTouchEvent/interceptTouchEvent/onTouchEvent.
6. TouchEvents: dispatchTouchEvent/interceptTouchEvent/onTouchEvent.
7. Animations support scale/rotate/translate，and will be performed before measure.
8. Dirty-Render: markDirty if next draw is necessary.
9. Supported Widgets:
   View, ImageView, TextView, Icon, ProgressBar, SVGView, ShaderView, Lottie, YUVVideoView, ScrollView, MovingArea, RecyclerView, Swiper, Loading, Switch, Radio, Picker, LyricView, FlexboxLayout, Page...
10. PlatformView:
    TODO!
11. Development:
    C++: See CppTest.cpp.
    React: https://github.com/tanpuer/skia-ui-react.
    SwiftUI: TODO!
12. Cross Platform
    Android: https://github.com/tanpuer/SkiaUI2