feat: include more data when copying messages as JSON (#5600)

src/messages/MessageThread.hpp

@@ -6,6 +6,8 @@
 #include <memory>
 #include <vector>
 
+class QJsonObject;
+
 namespace chatterino {
 struct Message;
 
@@ -62,6 +64,8 @@ public:
         return replies_;
     }
 
+    QJsonObject toJson() const;
+
     boost::signals2::signal<void()> subscriptionUpdated;
 
 private: