Make sure we only pack one copy of react-dom (#2603)
Make sure we only pack one copy of react-dom (#2603)

Fixes https://github.com/vector-im/vector-web/issues/2601
martindale/vector,vector-im/riot-web,vector-im/vector-web,vector-im/riot-web,vector-im/vector-web,martindale/vector,vector-im/vector-web,vector-im/riot-web,vector-im/riot-web,vector-im/riot-web,vector-im/riot-web,vector-im/vector-web,vector-im/vector-web