cold-path-server-podman: the Cold Path game server in a container

cold-path-server-podman is a new repository that runs the Cold Path multiplayer game server inside a Podman container, so no LuaJIT, LuaSocket, or LuaSec install is needed on the host. The upstream sources aren’t vendored — the image build pulls them from GitHub, and make build / make run / make logs handle the rest.