support react-native start

index.android.js

+require('./playground/index');

index.ios.js

+require('./playground/index');

scripts/start.js

   exec.killPort(8081);
   exec.execSync(`watchman watch-del-all || true`);
   exec.execSync(`adb reverse tcp:8081 tcp:8081 || true`);
-  exec.execSync(`node ./node_modules/react-native/local-cli/cli.js start --root=./playground`);
+  exec.execSync(`node ./node_modules/react-native/local-cli/cli.js start`);
 }