Make sure react always ends up in the commons bundle (#5192)
Make sure react always ends up in the commons bundle (#5192)

Fixes an edge case where some library imports react-dom by itself, like react-spring.
JeromeFitz/next.js,flybayer/next.js,azukaru/next.js,JeromeFitz/next.js,zeit/next.js,JeromeFitz/next.js,BlancheXu/test,flybayer/next.js,azukaru/next.js,zeit/next.js,flybayer/next.js,azukaru/next.js,BlancheXu/test,JeromeFitz/next.js,zeit/next.js,flybayer/next.js,azukaru/next.js,BlancheXu/test