Add add-on (DLC) support (#1519)

Add add-on content support

Co-authored-by: nmzik <Nmzik@mail.ru>

src/launcher/include/configuration.h

@@ -103,6 +103,7 @@ public:
 	QString    firmwareVer; /* requiredSystemSoftwareVersion from sce_sys/param.json */
 	QString    basedir;     /* Game base directory */
 	QString    game_path;   /* Launcher-unique game path */
+	QString    addons_dir;  /* Global setting; not saved per game. */
 	bool       custom_settings = false;
 	GameStatus game_status     = GameStatus::Unknown;
 	QString    game_comment;