Add support FrankerFaceZ badges. (#2101)

On startup, we poll https://api.frankerfacez.com/v1/badges/ids and store the mappings of user IDs to badges for the remainder of the applications lifetime.

src/singletons/WindowManager.hpp

@@ -14,7 +14,7 @@ class Paths;
 class Window;
 class SplitContainer;
 
-enum class MessageElementFlag;
+enum class MessageElementFlag : int64_t;
 using MessageElementFlags = FlagsEnum<MessageElementFlag>;
 enum class WindowType;