feat: add initial experimental Twitch Eventsub support (#5837)

Co-authored-by: nerix <nerixdev@outlook.de>

src/providers/twitch/eventsub/SubscriptionHandle.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "providers/twitch/eventsub/SubscriptionRequest.hpp"
+
+#include <memory>
+
+namespace chatterino::eventsub {
+
+struct RawSubscriptionHandle {
+    const SubscriptionRequest request;
+
+    RawSubscriptionHandle(SubscriptionRequest request_);
+
+    ~RawSubscriptionHandle();
+};
+
+using SubscriptionHandle = std::unique_ptr<RawSubscriptionHandle>;
+
+}  // namespace chatterino::eventsub