[Room] Set unread notifications to 0 manually

lib/src/Room.dart

@@ -611,6 +611,8 @@ class Room {
 
   /// Sends *m.fully_read* and *m.read* for the given event ID.
   Future<dynamic> sendReadReceipt(String eventID) async {
+    this.notificationCount = 0;
+    client?.store?.resetNotificationCount(this.id);
     final dynamic resp = client.connection.jsonRequest(
         type: HTTPType.POST,
         action: "/client/r0/rooms/$id/read_markers",

lib/src/StoreAPI.dart

@@ -92,6 +92,8 @@ abstract class StoreAPI {
 
   Future<void> forgetRoom(String roomID);
 
+  Future<void> resetNotificationCount(String roomID);
+
   /// Searches for the event in the store.
   Future<Event> getEventById(String eventID, Room room);