Limit chat message size

[roccodev]

This allows server owners to block oversized messages on the proxy's end.
They can either choose to kick the player or to just cut the message to fit within limits.

[tjalp]

I don't think this should be something built-in to Velocity, but rather something a plugin should do

[roccodev]

That's also something I was wondering, but Velocity already checks for invalid characters, and it also rejects oversized messages in the API's Player#spoofChatInput(String).