Update changelog.txt

Author: b-g

changelog.txt

@@ -12,6 +12,7 @@ New:
   + 20E3 extras-openmoji combining enclosing keycap by @nataliakeniganti #565
   + E420 to E435 extras-openmoji 🏳️‍🌈 Queer symbols by @felifluid Feli Berner #588
   + Chess pieces by @nataliakeniganti #605
+  + Ontario and Queretaro flag by @jj-marr #627 #628
 
 Improvements:
   * Emoji 17.0 changes