Fix webpack config (by stealing Dave's config)
Fix webpack config (by stealing Dave's config)

Without doing something like this it's hard to use `yarn link`ed resources.
vector-im/vector-web,vector-im/riot-web,vector-im/vector-web,vector-im/vector-web,vector-im/riot-web,vector-im/vector-web,vector-im/riot-web,vector-im/riot-web,vector-im/vector-web,vector-im/riot-web,vector-im/riot-web