fix: attempt to ensure our data stays synced

This is to try to stop extremely long sync times when opening the app
after a long period of not opening it.

Author: AKPWebDesign

app/src/main/java/tech/akpmakes/android/taskkeeper/MainActivity.java

@@ -147,6 +147,7 @@ private void updateUI(FirebaseUser user) {
 
         final Activity activity = this;
         mDBQuery = FirebaseDatabase.getInstance().getReference("events/" + user.getUid()).orderByChild("when");
+        mDBQuery.keepSynced(true);
         mAdapter = new FirebaseRecyclerAdapter<WhenEvent, WhenEventViewHolder>(
                 WhenEvent.class,
                 R.layout.item_whenevent,