add: bot bond selling

bot bond sell.py

@@ -123,6 +123,10 @@ def main():
         if message["type"] == "close":
             print("The round has ended")
             break
+        elif message["type"] == "open":
+             print("Market opened:", message)
+             market_open = True
+             place_bond_orders()  # open 받은 후에만 주문
         elif message["type"] == "error":
             print(message)
         elif message["type"] == "reject":