IOS supported now, ty it!

[rainyl]

I am happy to tell you that with a hackintosh, I finally made it to compile for ios, but still, I have no Apple devices, so not tested on iPhone, only on simulators.

opencv_dart.framework compiled by Github Workflow will be aviliable soon in v0.6.5, IOS developers can try it and tell me if it works on iPhone.

cd example
flutter pub get
flutter run -d iphone -v