Add a method for triggering the change of a comic cover from the model

Sad day for nice code.

YACReaderLibrary/db/comic_model.h

@@ -124,6 +124,7 @@ public:
     void reload();
     void reload(const ComicDB &comic);
     void resetComicRating(const QModelIndex &mi);
+    void notifyCoverChange(const ComicDB &comic);
 
     Q_INVOKABLE QUrl getCoverUrlPathForComicHash(const QString &hash) const;