Create first event handler and framework for it

rc_multiplayer/src/events/mod.rs

@@ -0,0 +1,6 @@
+mod validate_game_guid;
+
+pub async fn handler(init_ctx: &crate::InitConfig) -> crate::handler::LnlEventHandler {
+    crate::handler::LnlEventHandler::new()
+        .add(validate_game_guid::handler(init_ctx))
+}