Init scroll to eventid.

src/messageeventmodel.cpp

@@ -470,3 +470,12 @@ QVariant MessageEventModel::data(const QModelIndex& idx, int role) const {
 
   return {};
 }
+
+int MessageEventModel::eventIDToIndex(const QString& eventID) {
+  const auto it = m_currentRoom->findInTimeline(eventID);
+  if (it == m_currentRoom->timelineEdge()) {
+    qWarning() << "Trying to find inexistent event:" << eventID;
+    return -1;
+  }
+  return it - m_currentRoom->messageEvents().rbegin() + timelineBaseIndex();
+}