Add ignore for ServerKeepAlivePacket

[rtm516]

This adds ServerKeepAlivePacket as a packet to ignore as its likely not to be implemented soon and this will prevent it from spamming console with Could not find packet for ServerKeepAlivePacket

[Camotoy]

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same packet. How does Geyser manage this keep alive currently?

[Redned235]

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same packet. How does Geyser manage this keep alive currently?

It doesn't currently. I think we should instead handle this packet instead of ignoring it.

[Tim203]

If you ignore the packet for more then 30 seconds, you will time out. So it is already handled.

[Camotoy]

https://github.com/Steveice10/MCProtocolLib/blob/master/src/main/java/com/github/steveice10/mc/protocol/ClientListener.java is the link Tim sent me. Once the packet ignore list is alphabetized I'll approve this.