Add missing reactfx dependency
Add missing reactfx dependency

This had been getting pulled in transitively through the old
io.bisq.exchange:core artifact's parent pom. Now that we're depending on
the io.bisq:bisq-core, there is no parent pom in the mix anymore, and
the reactfx dependency must to be explicitly declared here.

bisq-network/exchange,bitsquare/bitsquare,bitsquare/bitsquare,bisq-network/exchange