refactor: Toast (#4899)

* Fixes a bug where avatars weren't loaded on fresh installations of Chatterino.
* Avatars now update every two weeks.
* Removes misleading `DownlaodManager` (now part of `Toasts.cpp`).
* Refactors usage of WinToast to be easier to read.
* Added version to AUMI.
* Removes manual `QString` → `std::wstring` conversions.
* Removes uses of implicit ASCII casts in `Toasts.cpp`, meaning it can be compiled with `QT_NO_CAST_FROM_ASCII`.

src/singletons/Toasts.hpp

@@ -24,14 +24,16 @@ public:
     static QString findStringFromReaction(const ToastReaction &reaction);
     static QString findStringFromReaction(
         const pajlada::Settings::Setting<int> &reaction);
-    static std::map<ToastReaction, QString> reactionToString;
 
     static bool isEnabled();
 
 private:
 #ifdef Q_OS_WIN
+    void ensureInitialized();
     void sendWindowsNotification(const QString &channelName,
                                  const QString &channelTitle, Platform p);
+
+    bool initialized_ = false;
 #endif
 };
 }  // namespace chatterino