add cordova 8 test scripts
add cordova 8 test scripts

ceisinger/cordova-plugin-firebase,DigitalsunrayMedia/cordova-plugin-firebase,DigitalsunrayMedia/cordova-plugin-firebase,arnesson/cordova-plugin-firebase,arnesson/cordova-plugin-firebase,ceisinger/cordova-plugin-firebase,ceisinger/cordova-plugin-firebase,ceisinger/cordova-plugin-firebase,arnesson/cordova-plugin-firebase,arnesson/cordova-plugin-firebase,DigitalsunrayMedia/cordova-plugin-firebase