docs(google-analytics): add missing docs
docs(google-analytics): add missing docs

ramonornela/ionic-native,klirix/ionic-native,xueron/ionic-native,xueron/ionic-native,ramonornela/ionic-native,ramonornela/ionic-native,xueron/ionic-native,driftyco/ionic-native,ramonornela/ionic-native,driftyco/ionic-native,klirix/ionic-native,driftyco/ionic-native,xueron/ionic-native,klirix/ionic-native