Matchcomms support

[Darxeal]

Getting and sending messages should be as simple as

std::vector<nlohmann::json> messages = matchcomms->GetIncomingBroadcast();

nlohmann::json message = ...
matchcomms->Send(message);

Libraries used are https://github.com/dhbaird/easywsclient and https://github.com/nlohmann/json/

This also should be backwards compatible with the example bot, meaning if someone updates their RLBotCPP submodule, it won't break their bot. However the matchcomms pointer would be nullptr, to actually use matchcomms they need to change one line in CppPythonAgent.py:

message = f"add\n{self.name}\n{self.team}\n{self.index}\n{game_interface.get_dll_directory()}\n{self.matchcomms_root.geturl()}"

I will add that in a PR when this is merged.

I'm not 100% sure about everything so feedback is welcome.