Update Stack Overflow tag in README
Update Stack Overflow tag in README

To better differentiate RNN questions from RN questions, we've switched to using the wix-react-native-navigation tag

wix/react-native-navigation,wix/react-native-navigation,3sidedcube/react-native-navigation,3sidedcube/react-native-navigation,3sidedcube/react-native-navigation,wix/react-native-navigation,wix/react-native-navigation,wix/react-native-navigation,3sidedcube/react-native-navigation,wix/react-native-navigation