This change will now allow for customizing the port number when running the metro server. The environment variable `RCT_METRO_PORT` can now be set when executing commands like `make run-ios`, `make run ios-device`, and `make run-android`. Though, it should be noted that `make clean` may need to be ran before attempting to set or change `RCT_METRO_PORT` since the react-native app will have statically built code that references the value of RCT_METRO_PORT from compile time and not runtime.