EasyAR SDK 2.2.1 fixes some compatibility issues with Android 8, iPhone XS/XS Max, and Unity 2018.

Detailed changes are as bellow,

+ improved security when connecting EasyAR CRS
* fixed ARSceneTracker crash when stop on Android 8 and later
* fixed black screen on Unity 2018 Android/iOS/Mac build
* fixed crash on iPhone XS/XS Max