Preview the challenger's lineup when receiving a challenge

[RonnyRoq]

When we're getting a challenge, we sometimes end up being requeuing straight away because of randoms piggybacking on a known team's lineup, or having 2/3 subs manually signed... which obviously takes an extra half hour to find. It would be really helpful to send the lineup when receiving a challenge from a team.

[RonnyRoq]

I've got a fix reusing your functions in matchmakingService.ts and interactionsUtils.ts, which basically sends the lineup when challenged, however I can't create branches on your repo to send a PR.