Summary:
Ignores `bundle.js` that is a webpack bundle and got most likely accidentally released. Already cherry-picked to 0.42
Fixes#12183
Closes https://github.com/facebook/react-native/pull/12185
Differential Revision: D4507535
Pulled By: mkonicek
fbshipit-source-id: 2ab404534b345cf531f408b654c34a30abd01458