Add thread root to timelime when starting a new thread (matrix-org#7983)

Author: Germain

src/components/structures/ThreadView.tsx

@@ -157,7 +157,7 @@ export default class ThreadView extends React.Component<IProps, IState> {
  private setupThread = (mxEv: MatrixEvent) => {
  let thread = this.props.room.threads?.get(mxEv.getId());
  if (!thread) {
- thread = this.props.room.createThread(mxEv);
+ thread = this.props.room.createThread(mxEv, [mxEv]);
  }
  thread.on(ThreadEvent.Update, this.updateLastThreadReply);
  this.updateThread(thread);