message: Explain setting of highlighted in room/$eventId showScreen handling.
diff: @@ -1118,6 +1118,7 @@ module.exports = React.createClass({
  const payload = {
  action: 'view_room',
  event_id: eventId,
  + // If an event ID is set (truthy), mark it as highlighted
  highlighted: Boolean(eventId),
  third_party_invite: thirdPartyInvite,
  oob_data: oobData,
  