Add missing __slots__ for Handshake packet

Author: ItsDrike

mcproto/packets/v757/handshaking/handshake.py

@@ -34,6 +34,8 @@ class Handshake(ServerBoundPacket):
     PACKET_ID: ClassVar[int] = 0x00
     GAME_STATE: ClassVar[GameState] = GameState.HANDSHAKING
 
+    __slots__ = ("protocol_version", "server_address", "server_port", "next_state")
+
     def __init__(
         self,
         *,