chore: add definition

Author: MichaelVerdon

packages/firestore/ios/RNFBFirestore/RNFBFirestoreModule.m

@@ -250,6 +250,9 @@ + (BOOL)requiresMainQueueSetup {
                   : (RCTPromiseResolveBlock)resolve
                   : (RCTPromiseRejectBlock)reject)
 {
+  FIRaddSnapshotsInSyncListener *addSnapshotsInSyncListener =
+  [RNFBFirestoreCommon getFirestoreForApp:firebaseApp databaseId:databaseId listenerId:listenerId]
+          .addSnapshotsInSyncListener;
   NSString *appName = [RNFBSharedUtils getAppJavaScriptName:firApp.name];
   NSString *firestoreKey = [RNFBFirestoreCommon createFirestoreKeyWithAppName:appName
                                                     databaseId:databaseId];