Identify custom clients (from Kaizo Network)

[M0REKZ]

Identify other Custom Clients the way Kaizo Network does and show a icon above the player, this does not need external servers since it will use some data that is sent to the teeworlds server and sent back to the client without being changed.

Currently it will show icons for Kaizo Network and Tater Client

This code is under normal DDNet license, it also has been contributed to chillerbot-ux (that client does not have a icon though)

This adds a new submodule https://github.com/M0REKZ/ddnet-custom-clients

Screenshot:

[SollyBunny]

I think this is a quite jank way of identifying clients as it would mean reshowing the flag when anyone else showing a flag enters

I would prefer using the flag to communicate with an external server which can do more than just identify your client