Add "reply in thread" timeline item action menu entry.

ElementX/Sources/Screens/Timeline/TimelineInteractionHandler.swift

@@ -24,6 +24,7 @@ enum TimelineInteractionHandlerAction {
     case displayErrorToast(String)
     
     case viewInRoomTimeline(eventID: String)
+    case displayThread(itemID: TimelineItemIdentifier)
 }
 
 /// The interaction handler groups logic for dealing with various actions the user can take on a timeline's
@@ -162,6 +163,8 @@ class TimelineInteractionHandler {
             let replyDetails = TimelineItemReplyDetails.loaded(sender: eventTimelineItem.sender, eventID: eventID, eventContent: replyInfo.type)
             
             actionsSubject.send(.composer(action: .setMode(mode: .reply(eventID: eventID, replyDetails: replyDetails, isThread: replyInfo.isThread))))
+        case .replyInThread:
+            actionsSubject.send(.displayThread(itemID: eventTimelineItem.id))
         case .forward(let itemID):
             actionsSubject.send(.displayMessageForwarding(itemID: itemID))
         case .viewSource: