Add a non REST API for bidirectional streaming.

[SR-Lut3t1um]

Edit:

As it turns out this is already possible, I was just experiencing a bug with Java's Project Loom.

Idea:

Add some sort of a bidirectional streaming api like gRPC or WS, maybe even pure HTTP2.

Why?:

Right now it's only possible to open one connection at a time. This means that it's not possible to listen to new events while e.g. creating a new game. This makes it nearly impossible to create a bot that's playing against multiple users at the same time. Also this would reduce the general HTTP overhead as there is no new HTTP handshake that's performed for every new request.

I'd also would like to help implement this if bidirectional steaming is wanted.