* Got RNTester building using XCode 11
* Updated JS to enable dark mode options on ios as well as mac.
* Initial port of RCTConvert
* Enable light/dark change reaction for background colors.
* Updated semantic colors for ios.
* Get macos target and ios target building again on XCode 10.
* Added DarkModeExample
* Implemented ios color fallbacks.
* Fallbacks working in iOS 12
* Cleanup
* Fixed target version back to 9
* Added Semantic color list to RNTester page.
* Refactor to use RCTPlatformDisplayLink instead of CADisplayLink as CADisplayLink is marked unavaible on Mac as of XCode 11.
* Fixed mac integation tests
* Fixed format-check issue
* Removed unused code from js. Updated comments in objC code.
* Removed UIColor alias and defined RCTUIColor for mac and ios.